Right, yeah, of course.
So, yes, the correct button is under 'Plugins' and it is 'export to .png' to get the files out. It'll ask you where you want them like downloading a file, and you can multi-select a bunch of them by shift-clicking and it'll extract them all.
View attachment 3395793
Dunno what a .tga is, don't use it.
When putting them back, you select 'Edit' from that menu which will bring up this mess.
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We want none of this... except for the 'Load' button, which will ask you to point at an image for it to load as the selected texture. Same deal as before, but you can't multi-select them (to the best of my knowledge) and obviously you have to be careful not to slot the wrong image in, so keep an eye on those names.
After you're done, hit 'Apply and save all' under the 'File' dropdown at the top.
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You can't overwrite anything you're currently editing, so either rename it or... huh, left to its own devices it adds .mod to the end, which functions perfectly well, but if you have that stupid 'hide file types' thing turned on, would it...?
...Uh, rename it, save it, then toss the original file and rename the modded one as the original. Toss the original first, since windows doesn't let you overwrite via renaming for some reason.