Here's a paracord retention loop added to my Mora HighQ Robust fixed blade knife.
I used a short length of paracord run through the slots on the pocket clip section of the molded sheath, and tied a two-strand Matthew Walker knot, with an added turn for a slightly lengthened/extended knot, to snugly slip over the knife handle, to help secure the knife in the sheath.
The knife fits in the sheath with friction and stays well enough on its own, but having the loop for retention just adds peace of mind that it will stay put.
I plan to eventually add some paracord to the sheath along with a firesteel, possibly a ranger band, and maybe drilling a hole in the knife handle to allow for a wrist lanyard too.
Lots of folks like to modify their Mora sheaths, some going further with making their own kydex or leather replacements or buying one from a custom maker, although the sheath may end up costing several time more than was originally spent on the knife. I've read enough comments and reviews on Mora knives to see that many view them as worth much more than what they paid for them... ;)