Absolutely! I'd say this is one of the top features of X3.mjau-mjau wrote: it loads extremely fast, something I am sure you have noticed and appreciate.
This is exactly what I imagined. I think the selection interface would fit nicely in the gallery settings besides "hide" and "set as preview image".Another option could be to "mark image for slideshow" from any gallery, and that would create a list of images (from multiple dirs) to use for the slideshow. However, this logic means there would only be ONE set of "marked images" that could be used in any gallery (or slideshow-intro), and we would have to create a "select" interface just for this "set".
Iirc in koken there were also only two of those selections available, you could mark an image with a star or a heart (there you already have the icons for putting this besides the flag and the eye ;) ).
I think you're right that copying images actually isn't that much work, but it just FEELS clumsy and maybe a little dated. Users are more used to GUI based interactions and although you can of course copy images in the X3 GUI it still feels a little bit like doing work in the console as compared to handling let's say a modern smartphone app.All this just to avoid copying a few select images directly into your slideshow-intro folder, which after all isn't too complicated. Not saying there aren't good options here, but just concluding the facts. Food for thought!
Thanks for sharing this interesting insights!