I run my multi-monitors with UltraMon (
www.ultramon.com). It's not free, but I've always felt I got the value I wanted from it. One of the abilities it possesses is to dictate where and how big a window opens up. It solves the Calibre issue you have raised. It opens up where ever Calibre wants to open up and then automagically moves to your desired position. Thus, it takes a fraction of a second longer to open and be ready to run.
Or we can wait for the doyens of Qt to hear your plea.
GM