It highly depends on what settings you want to change. A lot of it graphics settings cannot be changed without triggering a reload / loading screen. I imagine that may often be unacceptable, unless it’s only for like posed pictures with a dead raidboss post-progressionkill.
Most likely you’d be looking at a (flimsy) addon and not macro for something like this i suspect, or a pre-screenshot macro, followed by making the screenshot, followed by triggering a post-screenshot macro to flip things back down.
Also if you’ve just been dissapointed in the quality of your current screenshots, this may be the result of the default screenshot encoding settings, and not the actual game graphic settings.
Last i checked the default screenshot settings were to save as Jpeg (.jpg files), which is a lossy format, and aiming for retaining atleast/only 30% quality.
I’d start by either increasing the quality to 100% and/or switching to TGA (a lossless format). There are some issues apparently, with skyboxes on TGA screenshots i’ve heard, but i haven’t actually had a problem with it myself.
Either:
/console screenshotFormat tga
Or:
/console screenshotFormat jpg
/console screenshotQuality 10
Quality (1-10) with 10 being 100%, 5 being 50%, and so forth. I think 3 is the default.