I see my panel on all desktop thumbnails and I was under the impression that this was expected. Can you attach a screenshot that clearly shows the issue?

I have my panel on the right, which may make a difference. Attached is a screenshot.

Created attachment 147646 [details]
The panel on the right is not visible on focused desktop thumbnail

Ah! I see the issue. The focus outline is drawn inside the thumbnail rather than outside of it, so it completely covers skinny panels. Should be an easy fix.

Ah, is that what's going on? The panel is 40px wide, so not exactly skinny, but the outline should definitely be drawn around the thumbnail.

I made a merge request that fixes the issue. I will close this bug report as soon as it gets merged. https://invent.kde.org/plasma/kwin/-/merge_requests/3408

It'll happen automatically once the MR is merged if you add "BUG: 450963` to its own line in the MR description. See https://community.kde.org/Infrastructure/GitLab#Write_a_Good_Commit_Message.

Git commit 1f1e67f90be39460bd7f087c0c538545a092ccc1 by Nate Graham, on behalf of Niklas Stephanblome.
Committed on 09/01/2023 at 16:29.
Pushed by ngraham into branch 'master'.

effects/overview: Correct size of active virtual desktop highlight outline

The focus outline that highlights the active virtual desktop in the Overview effect, as
well as the half-transparent outlines that are around the other virtual desktops, cover
2 pixels on every side of every virtual desktop thumbnail.

This is because an invisible rectangle is used that has the same size as the thumbnail
and has a colored border, but borders are always drawn on the inside of QML rectangles,
so content in the thumbnail is covered up. Therefore, the width of the rectangle has to
be slightly adjusted to account for the thickness of the border.
FIXED-IN: 5.27

M  +1    -0    src/effects/overview/qml/DesktopBar.qml

https://invent.kde.org/plasma/kwin/commit/1f1e67f90be39460bd7f087c0c538545a092ccc1