Is there a way to make the info button from the View Toolbar appear even when a tiddler is being edited?

You will need to change quite some elements.

I did create a Field Editor plugin, which shows the tiddler info button in edit mode.

You can have a look at it. I was developed for something different so it may not work for you, but you can use it as a template.

The intro can be found at: [Intro] Multiline Field Editor Plugin
-mario