Right now it is being written alongside development from it. It is changing all the time, so information can fluctuate.
There’s already a stepping stone explaining some of the new options that are on the preview build of the new editor (Available on Alpha 4.11), which you can check here: https://outfox.wiki/dev/editor/0-Editor-Preferences/
For the basic stuff about adding notes, just press 1 through the number of columns available on the current game mode you’re on. Example: If you’re on dance, that would be 1-4, pump would be 1-5, popn can be 1-9, etc.
You can also get shortcuts about what keys to use by pressing F1 in the editor (It is planned to redo this entire screen too).