[FEATURE] Add additional text box to Multipliers for mod support

[jordan-dalby]

Is your feature request related to a problem? Please describe.
The settings available to the user at present are all from base game.

Describe the solution you'd like
It would be good if users could enter additional settings (by means of a large text box).

Describe alternatives you've considered
You can edit GameUserSettings.ini directly, so it's not a major issue, but a QoL improvement for sure.

Additional context
n/a