This would be a relatively rarely-used feature, but with the additional of docking indicators, automatic target indications, etc....it's very hard to take a clean screenshot these days. A command to take a screenshot in a convenient format (eg. PNG) with all UI elements removed would be of great use to modders wanting to showcase screenshots.

george moromisato 12 May 2021:

In 1.9 Beta 4 I added a command (F6) to show/hide the HUD. You can then take a screenshot as normal.