For 3.5.8 (still on the burner, should be out tomorrow),
I've reworked split text into view in panel.

Same code basically, but now you can set it to any open document, the panel is labelled, and there is a small close button.

One thing though.
I've been running into some problems with shortcuts.
Basically, drpython is not set up to handle more than one stc in a panel, for some keyboard shortcuts.

So What I have done is disable all non stc shortcuts in the View In Panel text controls.

I am not sure if in the future I will enable them, and make everything work, but for now, they are gone.

This is better than before, since operations like indent would not work properly.