I have never tried these solutions to cutting leggings, but here are a couple of ideas. (I wonder about wither abrasions - maybe use a fleecy band if necessary?) Best of luck!
(I don’t know if this board allows direct links, so replace the word DOT with a real “.” )
https://donkeysanctuaryofcanadaDOTwordpress.com/2018/06/01/big-bens-leggings/
https://www.instagramDOTcom/longhopesdonkeyshelter/reel/C76qnMjgnwu/