OpenMW-CS Manual

Previous OpenMW-CS Manual: http://downloads.openmw.org/opencs-manual/main.pdf

Current OpenMW-CS Manual: https://openmw.readthedocs.io/en/stable/manuals/openmw-cs/index.html

Note that you can switch between versions using the v: dropdown box at the bottom of the left column - "master" should be the latest.

Other possibly useful resources - written for vanilla Morrowind and TESCS:
Morrowind Mod Makers Manual

Scripting for Dummies