I tried my hand on a LB action to show, open and remove items from Safaris Reading List. Show and open them is not a problem. I also managed to remove items from the plist (row 61-65). It works temporarily. But something is missing.

readinglist.js

// LaunchBar Action Script

function run() {
    var plist = File.readPlist('~/Library/Safari/Bookmarks.plist')

    var listItems = plist.Children[3].Children

    var result = []

    for (var i = 0; i < listItems.length; i++) {
        var preview = listItems[i].ReadingList.PreviewText
        var title = listItems[i].URIDictionary.title
        var link = listItems[i].URLString

        result.push({
            title: title,
            subtitle: preview,
            icon: 'eyeglassesTemplate',
            action: 'options',
            actionArgument: {
                id: i,
                title: title,
                link: link,
                plist: plist
            }
        })

    }
    return result
}

function options(params) {

    return [
        {
            title: 'Open ' + params.title,
            url: params.link,
            icon: 'openTemplate'
        },
        {
            title: 'Remove ' + params.title,
            icon: 'removeTemplate',
            action: 'removeItem',
            actionArgument: {
                id: params.id,
                plist: params.plist
            }
        }
    ]
}


function removeItem(params) {
    // var newWebBookmarkUUID = LaunchBar.execute('/usr/bin/uuidgen').trim()

    // var plist = params.plist
    // var webBookmarkUUID = plist.WebBookmarkUUID
    
   

    // var i = params.id
    // var listItems = params.plist.Children[3].Children
    // listItems.splice(i, 1)
    // var plist = params.plist
    // File.writePlist(plist, '~/Desktop/testPlist.plist')

    // Does work only until sync kicks in. There are some parameters that need to be updated (WebBookmarkUUID, CloudKitDeviceIdentifier) … but I don't know how
    // Tried creating a new UUID … but that's not solving it

    // File.writePlist(plist, '~/Library/Safari/Bookmarks.plist')
}

When iCloud syncs the next time the deleted items reappear. I also tried changing the WebBookmarkUUID (manually as of now).
It probably shows that I am not a developer. Can someone help? Or is that impossible with this approach?