OBS could do that, I suppose. Add a screen capture source, and place a color source behind it sized 10px larger than the screen capture rect. Hit record.
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A while ago I did this by making a custom wallpaper with a box on it and set the capture region to the box.
I think Gnome can do this Built in but the only problem is this only works on GNOME obviously
I use peek for that
I use ffmpeg to record only the top left corner of my screen but I don't have any visual for it.
I used https://github.com/ftorkler/x11-overlay/ in the past for another tool, maybe this could help you.
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