So you are a smart one and figured out how to make your own arrowheads...
The help article tells how to do it (https://helpx.adobe.com/illustrator/using/stroke-object.html) and then the file itself has some instructions.

But then you try to save the changes, and get an error message. You can't overwrite the file, because it’s locked by Ai, because it uses it to display arrowheads in their dropdown...

Currently you have to save the file someplace else, close Ai, wait a bit, replace the fil, launch Ai back. Very cool...
Then you realize you made a tiny mistake probably, and you have to repeat the process, opening a saved copy (if you left a copy) and relaunch Ai again.

This is a wonderful and encouraging process to update presets! It’s like making pasta from the scratch each time you feel you need some more spices.

How about making the process of making custom arrowheads somewhat more humane?