Gentle prompt, its a UI change and new functionality so manual change also needed.
I actually haven't found anything in the documentation regarding the symbol tree (unless I missed it) so I'd have to write some new section about it. In my opinion, the tooltip says it all and there shouldn't be any need for any extra explanation.
Maybe we should consider what widget in the sidebar gets the focus by default - right now it's the entry (and the tree focus is just one tab or enter press away) but maybe users who use primarily keyboard are more used to having the tree focused. I don't mind much myself as I just use mouse for the tree.
I kept the focus as it is now - it seems to behave quite OK and and it would require moving
https://github.com/geany/geany/blob/0601c73f7a7abc40fe9ddbff6b906b0d0e5b5f79...
to `sidebar.c` so it has access to the tree to call `gtk_widget_grab_focus()` and also updating
https://github.com/geany/geany/blob/0601c73f7a7abc40fe9ddbff6b906b0d0e5b5f79...
None of it is a problem to do though if someone wants to focus the tree by default.