I think this is a regression from the 1.3 series, but I'm not entirely sure when I first noticed this. The issue is that, on Windows at least, 1.4 releases of Joplin no longer save and restore the window size. It's still an issue in 1.4.10, which I just installed this morning.
I noticed that there was a post about this issue from a year ago, but I didn't find anything more recent. Has anyone else noticed this?