Highlight the part of the GUI that has focus.

[audreytoskin]

It can be easy to miss that the text bar or something else still has focus. Perhaps the text bar, and/or the GUI buttons, could be highlighted a little more, so users don't wonder why the arrow key navigation isn't working.

[lehitoskin]

Not entirely certain how this would work from a technical standpoint - also how to make it work without it making the GUI look hideous.

[audreytoskin]

I could probably work out a pleasant-looking solution myself, if the Racket GUI used CSS...

For the GUI buttons, I sort of imagine a subtle "glow" effect, but I don't know if the Racket GUI library would support that.

The text bar might be easier to fix. Currently, when you start typing in the Edit Tags bar, the field turns yellow. Then it turns green when you save the tags. Maybe if the text bar is selected, but you have not started typing yet, there could be a different background color. Or the text could be set to bold or italic. Or the bar outline could be thicker or it could use a colored border.