I've never liked how calculation manager and various other EPM links open in pop up windows rather than tabs. Recently I hit that level of annoyance or boredom where I was actually bothered to do something about it so a quick search uncovered that it is quite easy to deal with in Chrome and the new Edge. There are options in Firefox as well but not so simple.
So next time you, for example, open Rules in PBCS and it opens up in a pop-up, simply right click in the title bar and click 'Show As Tab'. You'll then have a regular tab window that you can drag back to whatever main window you want.