[KevinH]

Wow. Okay. Let me investigate if we can use a keypress event routine to preprocess Shift-Tab as a focus change before it goes to CodeView.

Update:

Same issue happens on macOS as well. I so rarely use all keyboard so I never noticed it.

I also tried your red border qss file and it works nicely for BookBrowser, TableOfContents, and Clips Windows. Thanks you! CodeView already changes the current line background when it has focus so that is clear as well. Unfortunately Preview does not display any red border when it has focus. But since that is the only one that doesn't change, I know when it has the focus.

So the PreviewWindow probably has no border around it to change color as it is a QtWebEngineView.

Again something to add to the list to be investigated.