I never create a new symbol. I always copy one similar.
At tree view - right click - Save a Copy As…and I can give it a new name and select to what library to add it.
Symbols are usually pretty simple. The steps I followed for the first symbols I made are:
VERY IMPORTANT. Define a folder to keep your symbols in. You can’t (or shouldn’t) put them in the current Kicad Libraries. I think you can do this from symbol editor.
Open the Symbol editor.
“N” for new symbol.
Place a pin or two.
Save it to your new library. Do this with only a few pins to be sure you can save it properly before you put a lot of effort into the symbol.