I am currently flying some flight plans that follow the old Route 66 road in the US. I don't have the fortitude to do them in a single setting, so what I do is land at an airport somewhere near a waypoint, delete all of the previous ones, and save out a new plan for "next time". (These FP's have hundreds of WPs, so that the alignment of the Mother Road can be accurately followed.)

The problem is, the author of these flight plans uses waypoint numbers to describe interesting things on the flight (this is the one I'm doing right now: https://flightsim.to/file/5983/get-your-kicks-above-route-66-oklahoma-3). But LNM resets the WP numbers to start with WP1 when I delete the WPs I've flown over, so it's not straightforward to follow his route description.

This might be a corner case that would not be taken advantage of by other pilots, but I thought I'd bring it up.

Renumbering is only done for waypoints starting with "WP". Others are not touched.

You can change the names manually in LNM to something else but this is a bit cumbersome and there is no bulk edit.
Maybe it is easier to load the LNMPLN file into a text editor (it is a XML text file) and do a search and replace of "WP" with something else.

Alex