I must be misunderstanding what it is you want to do. As a test, I opened two images in GIMP. On the smaller one, I ctrl-c. Tabbing over to the larger one, I ctrl-v. The small image is overlaid in a temporary layer on top of the larger one. I can drag it around with the move tool. At this point if I'm done I can just export it. If I need to do more work I can either flatten it with Layer -> Anchor Layer or make the new layer permanent with Layer -> To New Layer.
I don't see how it could possibly be simpler than that. Even the exact same keyboard shortcuts you used in MS Paint work directly in Gimp with no changes!
Ok, I just tried this in gimp and crtl+C and ctrl+V do not work for me. When I right click on the other window with all the layers listed, it sees that there is another layer in there with another picture, but it will not show up in the resultant image.
I'm going to be honest, I'm not a daily gimp user. Even the terms you've used here (flatten, anchor, export, tabbing over, temporary, move tool, permanent) will require me to google those terms.
I'm sure that the shortcuts that I've used 'work' for you. However they do not 'work' for me. Like, I'm honestly going out of my way here to test this out and trying to follow what you've written there. I'm spending my own time to try this. I know what AWS is, I know Python and pandas fairly well, I've gone to talks by Stallman, etc. I'm not grandma.
And I have no idea what to do here or what you're trying to tell me.
Gimp, for me, a semi-tech-literate person, is gobbly-gook and requires loads of training to get up to speed.
I think any complexity in my explanation is probably inherent to a layers-based graphics program, and probably can't be further reduced. The "tab" part of it works exactly the same as every browser in existence. (Are you using an ancient version of Gimp without tabs or single-window mode? The latest is 2.10.)
I'm also not sure what you're talking about with right-clicking, since the instructions I gave don't require you to click on the image at all.
If ctrl-c on one image, ctrl-v on another doesn't put the first image on top of the second for you, it would probably be helpful to report a bug to the Gimp folks because that's always worked for me and surely ought to work. (Obviously if you're on MacOS or something the key might be different, cmd-c or something.)
I don't see how it could possibly be simpler than that. Even the exact same keyboard shortcuts you used in MS Paint work directly in Gimp with no changes!