How to mix 2 blender files in just 1?

In one file I have a model that I’ve been adding actions and animation to, in another file I just received an updated version of the model, I need to copy all the actions I did in the first model to the second model; they have both the same names in bones and stuff, except the 2nd one has more stuff. How can I mix these 2 files in just 1 that has the new model with the actions from the old one?

you can append the actions to the new file with Shift F1
navigate to the file and chose the actions you want to append

what you might find useful is to create one file for the model
and one for the animation and “link” the model to that file
that way you can create multiple animations with the one model
and if you update the character - it will also update in all the other files