Hi Wedrownik, you actually can, with some recommendations.
You can first export a json from the project you want to bring into the other. Then import it using import data, and choosing the same skeleton:
Import - Spine User Guide: Data
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Next you can import the spine file and choose the animations you want to import. (you can use ctrl or shift to select them all at once)
Import - Spine User Guide: Animation
BUT you need to be careful: the bones of both projects need to have unique names that don't overlap across the two skeletons. The same goes for images, slots, etc. or the import may go wrong. The same goes for the animations.
But let's rediscuss this idea first: perhaps you don't need to import the spells for each character, you could simply import them as two separate skeletons in the same project to ease the animation syncing of the effects, but just match their roots at runtime overlapping the vfx on the characters. Otherwise you may be needlessly repeating identical data across all the projects.