I've a textbox control (drag-dopped via the "Insert Control" tab) on my workspace. But since that control has no name or ID, I was wondering if I could target that control via Javascript API to get or set its value. Is this even possible?
The JS API interacts with the UI based on object field name, so your easiest option is a custom field that exists on the workspace object; then you can populate it as per the docs. If you don't want to keep the data, then you could implement a Custom Process Model to remove the info from the record on save. Another option would be an addin that displays a browser control where you implement an alternative to the JS API and use the add-in to populate data in your workspace controls directly.