Change Move Mastery (by Move Tutor) in PLA PKHeX editor?

[sternens_lapis]

Hi,
I was wondering, is it possible to change a move to be mastered as if by Move Tutor (Seed of Mastery)?
For context; I want to make a legal level 21 Wyrdeer (which as far as I know is the lowest legal level it can be).

My idea was to take a Stantler from the encounter database, change it's level to 21, at which point it gets access to Psyshield bash and have it master the move as if by Move Tutor to be able to be able to make a level 21 Wyrdeer. 
Pretty sure this in theory should be able to work in-game and be legal, but when I attempted to create a pkhex file for it I couldn't find an option to manually change the mastered status of the moves. Psyshield bash doesn't show up in the move shop menu (I assume because it's learned naturally).
I tried looking for a way to change it, but was unable to find one, also couldn't find any forum posts. I might just be overlooking something obvious.

Is there a way to change the Mastered status of a move manually? Did I just miss it? Or is this not possible? 
I'm looking forward to learn if my idea is even possible and/or how to execute it. Any tips, help or feedback is welcome.

Yours faithfully,
Lucy

(This time posted in the right place hopefully, previously accidentally posted under saves - editing help instead of legality subforum, sorry about that i am dumb)

899 - Wyrdeer - AC17C3BDCC86.pa8

[Kaphotics]

The move shop button is right there. Give it a try.

Hint: form argument tracks usage.

[sternens_lapis]

Thanks for the help,
The form argument is at 20.
Regarding the move shop menu, I might be missing something, but I can't find Psyshield Bash as an option in the move shop list. 

- Lucy

[Atrius97]

To my knowledge, not every move can be mastered with a Seed of Mastery, (specifically moves not found in the Move Shop and learned via Level Up)

Quote

Pretty sure this in theory should be able to work in-game and be legal

Try testing it ingame to see if it's actually possible, the mechanics don't always work the way you expect. 

Edited July 26, 2022 by Atrius97

[sternens_lapis]

Thanks, I did some more additional research and it does seem like only moves taught outside of level up movesets can be mastered using the seed of mastery. This wasn't clear to me through the in game item description. 

- Lucy