certain moves u can't do that with like mario's fire ball i think or zelda's side b but try and see what works. but yes u can swap moves that way but u also need to swap animations to match up
Well, there's more than just this. If you want to swap entire movesets, search up the clone engine. Single moves are another thing. In Project Smash Attacks, copy a special of one character and paste into another. However, some characters use articles. As stated by zigheart, Mario's fire ball is special. When veiwing a special in PSA, avoid things that say stuff like:
Generate Article: 2
I believe it is possible to swap articles, however...
You also need to copy all of the animations. Sometimes this can be difficult because some specials use multiple animations to start, charge, use, and end the attack. Others use few animations. You also might want to use the same Main, GFX, SFX, and Other parts of the special in the Sub Actions tab in PSA. Sometimes articles are used here, also.