Was it of sufficient speed for your needs? It certainly takes longer to open than a couple of milliseconds. But I'm not aware of any GUI application that does.

Not that I would actually notice anyhow, given display latency of ~16ms at 60 Hz anyways :D

However I have seen mystery hangs in general, which can happen to almost anything.

I had a machine one time where a self-built version of midnight commander would always hang for several seconds on startup. Never saw that before or since. You can not say "mc takes something like 5-10 seconds to start up" even though it did on that machine that time.

I don't remember the details, but it turned out to be some combination of environment/context ie a particular terminal on a particular client sshing to a particular server where mc itself was, env variables, and/or setting in a mc config file. Might have been something to do with locale or TERM, or.. . I really have no idea anymore. But the hang was fixed by hunting down the config problem, and I've never seen it before that, nor since.

Following Geany updates fixed the issue, as far as I remember.

I suppose it could load the interface first, then load the files, then parse and highlight them after the window is up, but don't feel like it would make a lot of difference until its done.

You may find projects useful. Can open the dozen files for one project, then close it, then open the next group from another project. Instead of every file you potentially might want to work on.