Geany does not help me to access those files quickly. I have to think which ones are affected and open them manually.
Agreed, but in fact Geany does not know about those files either, it only regularly tests the current file. This is to reduce the cost of regularly `stat`ing lots of files which can be an expensive operation, especially if the user has many files open, and/or if files are on remote servers. And some users have a LOT of files open, and as home file servers get cheaper more use "remote" servers.
There was an attempt to use the GIO file monitoring which may have been able to handle more files efficiently, but it proved to be unreliable, triggering multiple times and causing the infobar to come back repeatedly. This may not neccessarily be GIOs fault since the underlying OS `inotify` interface notes the possibility of missing or repeated events. This code is still in the Geany source but `#if`ed out, anybody is welcome to try to sort it out.
it would be great to put the deleted files up front,
Even if monitoring worked, its considered bad UI design to reorder a users tabs. Other methods of indication could be used to allow the user to find such files quickly.