I don't know but wouldn't it be better to do it the other way round - i.e. display the file name and line number directly in the list as before and show the signature as a tooltip? What I get right now doesn't seem very useful and if you for instance want to navigate to `gpointer data`, one would have to go through many items in the list below and wait for the tooltip to appear to locate the right one.
<img width="694" alt="Screenshot 2023-08-13 at 21 01 42" src="https://github.com/geany/geany/assets/713965/cbc54ce1-3062-44b4-bf99-0a4620d59dba">