What do the characters at the bottom of the sidebar mean?

Short Answer

That is the version marker. It names the build of Picasi that is currently running. When you report a problem, support uses it to tie your report to the right build.

Details

Where it sits

At the very bottom of the sidebar, below the user menu, in small grey type. It is made up of the build number and the first seven characters of the commit, for example 20260921.1830 · a1b2c3d.

Point at the marker with the mouse, or move to it with the tab key:

Commit — the full identifier of the build
Deployed — when this build was rolled out
Worker restarted — when the server picked it up

When an amber dot sits in front of it

The tooltip then adds: The worker has not restarted since the deploy. The new build is rolled out, but the previous one is still being served. If something stops working at the same time, contact support and quote the marker.

What support needs it for

On a bug report the marker says which build you were on. That narrows down whether the problem belongs to a particular build or happens regardless of it.

If that doesn’t help

The marker is a read-out, there is nothing to set on it. If something is not working, the support chat takes it from there — quote the marker when you write.