Credit to: @shabegom - Add a block ref to the current line by adding a ^uniqueId on the end and copying to the clipboard the embed reference link so you can quickly paste the block ref somewhere else in your vault. Similar to Roam ctrl + click and drag to create block ref.

obsidian.templater.create-and-copy-block-ref-id.js

<%*
//v1.1: Changed to using the new "view.editor" instead of deprecated "view.sourceMode.cmEditor"

let cmEditorAct = this.app.workspace.activeLeaf.view.editor;
let curLine = cmEditorAct.getCursor().line;
cmEditorAct.setSelection({ line: curLine, ch: 0 }, { line: curLine, ch: 9999 });

function createBlockHash() {
    let result = '';
    var characters = 'abcdefghijklmnopqrstuvwxyz0123456789';
    var charactersLength = characters.length;
    for ( var i = 0; i < 7; i++ ) {
        result += characters.charAt(Math.floor(Math.random() * charactersLength));
    }
    return result;
}

let id = createBlockHash();
let block = `![[${tp.file.title}#^${id}]]`.split("\n").join("");
navigator.clipboard.writeText(block).then(text => text);
tR = tp.file.selection() + ` ^${id}`.split("\n").join("");
%>

Line 6 tries to move to position 9999 of the line which is beyond the end of you file. If you change the 9999 to the word Infinity

If you change the 9999 to the word Infinity

It works. Thanks

Hello, I found this template recently and decided to add a regex to simply copy the block when it already has a reference. Leaving it here in case anyone find it useful.
I ended up following shabegom guide so I will leave it here as reference for those that are writing scripts directly on the template file. https://shbgm.ca/blog/obsidian/how-to-use-templater-js-scripts

function createAndCopyBlockRefId(tp){
  const editor = app.workspace.activeLeaf.view.editor
  const cursorLine = editor.getCursor().line
    
  editor.setSelection({line: cursorLine, ch: 0}, {line: cursorLine, ch: Infinity})

  const textBlock = tp.file.selection();
  const regex = /\^[a-zA-Z0-9-]+(?!.*\^[a-zA-Z0-9]+)$/

  const match = textBlock.match(regex);

  const id = match ? match[0] :  `^${createBlockHash()}` ;
  const block = `![[${tp.file.title}#${id}]]`.split("\n").join("");

  navigator.clipboard.writeText(block).then(text => text);
  return textBlock +  (match ? '' : `^${id}`.split("\n").join(""));
}

function createBlockHash() {
    let result = '';
    var characters = 'abcdefghijklmnopqrstuvwxyz0123456789';
    var charactersLength = characters.length;
    for ( var i = 0; i < 7; i++ ) {
        result += characters.charAt(Math.floor(Math.random() * charactersLength));
    }
    return result;
}

module.exports = createAndCopyBlockRefId