Yes, you can use pkhex for that...
Backup your game using checkpoint/jksv and put your sdcard into your pc. Run pkhex and open your save backup. Navigate to the box where that pokemon is and right click on it and select view. Once it is showing (you will see the sprite for it in the upper center area, select OT/Misc tab (fifth one) and change the OT, SID, and TID there. After you enter your information, right click over the pokemon and select set. Export the game save to the sdcard install the card into your switch, boot into cfw, restore the save with checkpoint/jksv, start up pokemon sv, and done...