Another one I don’t know: can you embed a gimp file into a layout editor? A common workflow is to embed a photoshop file into an indesign file; you can then edit your photoshop file and have your indesign file updating automatically. This is a common workflow in several adobe products, eg I believe after effects sequence embedded into a Premiere timeline is possible/common.
You sure can. I'm not even an artist and that's the one part of GIMP I can speak for. It has its own Python library, so almost anything you can do in editor you can do programmatically, but I made a few scripts for batch processing an entire album of images.
(documentation is about as awkard as the GUI, though. You will eventually find what you need after putting in 3-5x more effort than what should have been necessary, but it's somewhere in the docs)