Plugin Files And You (ESM/ESL/ESP)
Beginning with Patch 1.5.3 of Skyrim Special Edition, the game supports a new type of mod file known as a "light plugin" with the .esl extension. Elminster has spent a considerable amount of time studying how this works and has had a number of community members aid in verifying this information. Since questions about new plugin types come up all the time, I felt it was best to make sure our source here is accurate.
Flag Types
Plugins can have 3 different flag types: ESP, ESM, and ESL.
I went in and did some checking to be sure of how vanilla overrides behave in various files. This is the load order I used:
There are gaps in the index numbers because I redacted the rest of the mods from the list for brevity.
When altering forn 00109112 (a book) the text I changed it to showed up as expected. 62 overrides everything else, 14 overrides all above it, 13 overrides, etc. The vanilla form is overridden exactly in the order these mods are positioned, and if they are rearr