Delete if this isn't something you guys want on the forums, but...
For those who'd like something more powerful than this GREAT suggestion from Hyperstrike, I've been using this photo editor for decades now (and by use I mean like 1% of what it does) and it makes screenies real easy to do while in-game. The link is something I just now found when looking for something "fair use" (this is old, but modern) as they make new versions and retire support for old ones over time. When configured, you can simply use the toolbar controls in the app to activate a continuous screen-shot function (each combo keypress = a new image) that works independent of the OS's or the Game's keybinds.
Imma go cry now because this is Newer than my version. >.<