Minify XML generated by Blockly.

blockly-minify.js

(function minifyXML(source) {
    source.value = source.value.replaceAll(/\n */g, "");
    source.select();
})(document.querySelector("#content_xml"));
/* 
    Blockly {
        https://scratch.mit.edu/discuss/topic/491165/
    }
    Context {
        https://scratch.mit.edu/discuss/post/4990156/
    }
    To test {
        Navigate to <https://blockly-demo.appspot.com/static/demos/code/index.html>,
        view the "XML" tab,
        then paste the code
    }
*/

blockly-minify.min.js

javascript:(function minifyXML(source){source.value=source.value.replaceAll(/\n */g,"");source.select()})(document.querySelector("#content_xml"));

index.html

<style>
    textarea {
        width: 500px;
        height: 200px;
    }
</style>
<textarea id="content_xml"><xml xmlns="https://developers.google.com/blockly/xml">
  <block type="text_print" id="kKf,GaluJo~ApYPxGGjn" x="113" y="163">
    <value name="TEXT">
      <shadow type="text" id="hL19Vek;njuYt?P7..P`">
        <field name="TEXT">abc</field>
      </shadow>
      <block type="text" id="5xy/0L@a]QqKt]ETW@{6">
        <field name="TEXT">Hello, world!</field>
      </block>
    </value>
  </block>
</xml>
</textarea>
<br>
<button id="minify">Minify</button>

test-example.dart

import 'dart:html';

void minifyXML(TextAreaElement source) {
    source.value = source.value?.replaceAll(RegExp("\n *"), "");
    source.select();
}

void main() {
    (querySelector("#minify") as ButtonElement).addEventListener("click", (_) {
        minifyXML(querySelector("#content_xml") as TextAreaElement);
    });
}

https://dartpad.dev/795755a753472371f816f426917044aa?null_safety=true