Application Studio - Insert Text at Cursor location

I want to add a button next to the Text Area that would pass the current text and cursor index to a function, the function inserts text at a specified location, and returns the result. Any ideas on how I can insert text at the cursor’s location in a Text Box/Text Area?

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With a classic customization I could use the SelectionStart property to get the index of the cursor, and insert at that point in the string. Is there some Javascript or something I can use within Application Studio to achieve the same thing?

I don’t think so :cry: