Need help: Starting new set, want to add new mana symbol

Hello!

I am trying to make a few cards testing an idea for a new mana-related mechanic, kinda similar to Snow mana. 

Naturally, I need to edit the code to allow MSE to recognize this symbol.

First of all, I am using the MSE 2.1.2 from the Additional Resources above. (Not the advanced, just the regular)

My card style is M15 Style, and symbol set selected is M15 Normal.

I have created a symbol for my mana mechanic, and added it to the folders magic-mana-large.mse-symbol-font and magic-mana-small.mse-symbol-font.

I have adjusted the Scripts in each of these folders such that it has a new defined symbol (Letter chosen is F).

Tested in MSE, it shows in the Insert Symbol dropdown menu just fine.

However, my problem arises when I attempt to get the symbol to show up when simply typing out cards.

As far as I know, all the card regex is handled by the script file in magic.mse-game. The problem is, when I attempt to add "F", nothing happens in the editor. 

The code is far too complicated for me to properly understand, and I am not familiar with regex to begin with.

I have been adding F to every location I believe it makes sense to - right after any mention of the Snow mana symbol, S.

For example:
mana_sort := sort_text@(order: "\\?XYZI[0123456789]VLHSFCAIE(WUBRG)") This, unfortunately, does not work.

Putting the letter F into the casting cost of a card in MSE results in nothing.

Putting the letter F into the text box of a card in MSE results in it disappearing and no symbol appearing.

How do I need to edit this file to make it work correctly?

P.S. I have also noticed that attempting to add the Energy symbol has a similar issue.