Well, I already answered, that I just duplicated and removed frames from existing SLD files, which is much easier to do than encode/decode images to/from SLD.
I am also waiting for Tevious to update SLX Studio, because I want to change some graphics without being hindered by SMX palette restrictions but I have no idea how long is it gonna take him because he has his work and other modding project on higher priorities.
Btw, Spriteblood managed to import unit, tree, etc graphics from SLD files to his Overreign mod, so if you are interested, you can ask him how he did it in his Discord server