I feel like an idiot for not being able to follow this tutorial, but it seems things have changed. https://youtu.be/Q9f-WVs3ghI?t=1013
I dont want to follow the tutorial exactly because the FlipNames has changed, it leaves the .001 extension.
If I select W>symmetrize parent bones stay on the left side, and only the children bones are copied(and parented to the left side).
Here's the file https://tinyurl.com/y99pl9dt
