I just upgraded from QB Desktop 2016 to 2019. The IIF import process now requires that all windows be closed before doing the import. This is really annoying. If the process is going to close the windows it should put them all back when it's finished. You could also offer an option on the Window menu to save the current window layout and restore it later.
I keep 6 or 8 windows open all the time as a financial dashboard and for quick access to accounts, etc. Having to go reopen all those windows every time I do an import (which I often do several times a week) is a big, needless hassle.