The plugin adds a breadcrumb navigation below the pagetitle for easier navigation/orientation.

ppb_managerBreadCrumbs.plugin.php

<?php
/*
    ppb_managerBreadCrumbs for modx 2.3.x
    Version: 0.1
    
    original plugincode written by @argnisto  
    frankensteined by info@pepebe.

    Description: The plugin adds a breadcrumb navigation below the pagetitle 
    for easier navigation/orientation.
    
    Note: Most of the code was shamelessly frankensteined from modDevTools by argnist.
    modDevTools can be installed by modx package manager. Try it, its a very useful plugin.
    The complete code for moddevtools is hosted on github: https://github.com/argnist/modDevTools
    
    If you want to have breadcrumbs, but you don't need the rest of modDevTools, 
    this will do the job.
    
    Usage: Copy code into a new plugin (ppb_managerBreadCrumbs) and set it to OnDocFormPrerender. Done.
    
    2do:
    Rewrite the whole thing and get rid of stuff we don't need.
    
*/
$debug = false;

$limit = 3;

if($modx->event->name != 'OnDocFormPrerender') return;

if(!function_exists('writeToLog')){
    function writeToLog($msg,$debug){
        if($debug){
            $modx->log(modX::LOG_LEVEL_ERROR, '[managerBreadCrumbs] moddevtools plugin ' .$msg);
        }
        return;
        
    }
}

if(is_object($modx->getObject('modPlugin', array ('name' => 'modDevTools', 'disabled' => 0), true))){
    $msg = 'installed and active. No need for additional breadcrumbs';
    writeToLog($msg,$debug);
    return;
}
else {
    $msg = 'either not installed or deactivated. Lets have our own breadcrumbs';
    writeToLog($msg,$debug);
}

$config = array();

if(!function_exists(getBreadCrumbs)){
    function getBreadCrumbs($resource,$modx,$limit) {

        if (($modx === modSystemEvent::MODE_NEW) || !$resource) {
            if (!isset($_GET['parent'])) {return;}
            // $resource = $modx->getObject('modResource', $_GET['parent']);
            if (!$resource) {return;}
        }
        
        $context = $resource->get('context_key');
        if ($context != 'web') {
            $modx->reloadContext($context);
        }
        
        $resources = $modx->getParentIds($resource->get('id'), $limit, array( 'context' => $context ));
        
        if ($modx === modSystemEvent::MODE_NEW) {
            array_unshift($resources, $_GET['parent']);
        }
        $crumbs = array();
        $root = $modx->toJSON(array(
            'text' => $context,
            'className' => 'first',
            'root' => true,
            'url' => '?'
        ));
        $controllerConfig = $modx->controller->config;
        $action = $controllerConfig['controller'];
        if ($action == 'resource/create') {
            $action = 'resource/update';
        }
        if (isset($controllerConfig['id'])) {
            if ($controllerConfig['controller'] == 'resource/create') {
                $actionObj = $modx->getObject('modAction', array('controller' => 'resource/update'));
                $action = $actionObj->get('id');
            } else {
                $action = $controllerConfig['id'];
            }
        }
        
        $modx->log(modX::LOG_LEVEL_ERROR, '[managerBreadCrumbs] action: ' . $action);        
        
        $isAll = false;
        for ($i = count($resources)-1; $i >= 0; $i--) {
            $resId = $resources[$i];
            if ($resId == 0) {
                continue;
            }
            $parent = $modx->getObject('modResource', $resId);
            if (!$parent) {break;}
            if ($parent->get('parent') == 0) {
                $isAll = true;
            }
            $crumbs[] = array(
                'text' => $parent->get('pagetitle'),
			    'url' => '?a=' . $action . '&id=' . $parent->get('id')
            );
        }
        
        $modx->log(modX::LOG_LEVEL_ERROR, '[managerBreadCrumbs] crumbs: ' . print_r($crumbs,true));        
        
        if ((count($resources) == $limit) && !$isAll) {
            array_unshift($crumbs, array(
                'text' => '...',
            ));
        }
        // Add pagetitle of current page
        if ($modx === modSystemEvent::MODE_NEW) {
            $pagetitle = $modx->lexicon('new_document');
        } else {
            $pagetitle = $resource->get('pagetitle');
        }
        $crumbs[] = array('text' => $pagetitle);
        $crumbs = $modx->toJSON($crumbs);
        
        //$modx->controller->addJavascript('../assets/components/ppb_managerBreadcrumbs/js/breadcrumbs.panel.js');

        $tpl = "
            <script id='managerBreadCrumbs_tpl' type='text' data-plugin='managerBreadCrumbs'>
                <tpl if=\"typeof(trail) != 'undefined'\">
                    <div class='crumb_wrapper'>
                        <ul class='crumbs'>
                            <tpl for=\"trail\">
                                <li {[values.className != 'undefined' ? 'class=\"'+values.className+'\"' : '' ]}>
                                    <tpl if=\"typeof url != 'undefined'\">
                                        <button type='button' data-url='{url}' class=\"controlBtn {[values.root ? ' root' : '' ]}\">
                                            {text}
                                        </button>
                                    </tpl>
                                    <tpl if=\"typeof url == 'undefined'\">
                                        <span class=\"text{[values.root ? ' root' : '' ]}\">
                                            {text}
                                        </span>
                                    </tpl>
                                </li>
                            </tpl>
                        </ul>
                    </div>
                </tpl>
            </script>
        ";
        
        $modx->controller->addHtml($tpl);

        $panel = "
            <script type='text/javascript' data-plugin='managerBreadCrumbs'>
            var modDevTools = function(config) {
            	config = config || {};
            	modDevTools.superclass.constructor.call(this,config);
            };
            Ext.extend(modDevTools,Ext.Component,{
            	page:{},window:{},grid:{},tree:{},panel:{},combo:{},config: {},view: {},utils: {}
            });
            Ext.reg('moddevtools',modDevTools);
            
            modDevTools = new modDevTools();
            if (typeof modDevTools.modx23 == 'undefined') {
                modDevTools.modx23 = typeof MODx.config.connector_url != 'undefined' ? true : false;
            }
            
            modDevTools.BreadcrumbsPanel = function(config) {
                config = config || {};
                Ext.applyIf(config,
                    {
                         bdMarkup: document.getElementById('managerBreadCrumbs_tpl').innerHTML
                        ,bodyStyle: {background: 'transparent'}
                    }
                );
                modDevTools.BreadcrumbsPanel.superclass.constructor.call(this,config);
            }
            
            Ext.extend(modDevTools.BreadcrumbsPanel,MODx.BreadcrumbsPanel,{
                onClick: function(e) {
                    var target = e.getTarget();
                    if (typeof target != 'undefined') {
                        var url = target.getAttribute('data-url');
                        if (url) {
                            MODx.loadPage(url);
                        }
                    }
                }
                ,_updatePanel: function(data){
                    this.tpl.overwrite(this.body, data);
                    var \$this = this;
                    setTimeout(function(){
                        \$this.ownerCt.doLayout();
                    }, 200);
                }
                ,getPagetitle: function(){
                    var pagetitleCmp = Ext.getCmp('modx-resource-pagetitle');
                    var pagetitle;
                    if (typeof pagetitleCmp != 'undefined') {
                        pagetitle = pagetitleCmp.getValue();
                        if (pagetitle.length == 0) {
                            pagetitle = _('new_document');
                        }
                    } else {
                        pagetitle = '';
                    }
                    return pagetitle;
                }
            
            });
            Ext.reg('moddevtools-breadcrumbs-panel',modDevTools.BreadcrumbsPanel);

            Ext.onReady(function() {
                var header = Ext.getCmp('modx-resource-header').ownerCt;
                header.insert( 1, {
                    xtype: 'moddevtools-breadcrumbs-panel'
                    ,id: 'resource-breadcrumbs'
                    ,desc: ''
                    ,root : {$root}
                });
                header.doLayout();
                var crumbCmp = Ext.getCmp('resource-breadcrumbs');
                var bd = { trail : {$crumbs}};
		        crumbCmp.updateDetail(bd);
		        Ext.getCmp('modx-resource-pagetitle').on('keyup', function(){
                    bd.trail[bd.trail.length-1] = {text: crumbCmp.getPagetitle()};
                    crumbCmp._updatePanel(bd);
                });
            });
            </script>";
        
        $modx->controller->addHtml($panel);
    }
}

getBreadCrumbs($resource,$modx,$limit);

return;