I've compiled a list of Spell ID numbers that are currently claimed by published mods. This will work til NullCascade is able to add something official to MWSE.

https://docs.google.com/spreadsheets/d/1xRoWcm6iI2jqMVxI9A5q2E2FbIY-I9CiXm7oBIptO0Q/edit?usp=sharing

If you publish anything, let me know and I'll add it.