Add Toggleable Custom Prompt Fields to Preset

[rankcody]

Is your feature request related to a problem? Please describe.
Some prompts work better when used sparingly rather than being used all the time (ex. NSFW prompts, CoT prompts, style prompts, etc.). However, it is inconvenient to constantly edit the preset to add and remove these prompts when needed. The interface could stand to better accommodate the use case of a prompt that is not always being used.

Describe the solution you'd like
The ability to add custom fields for prompts to the preset, in addition to the system/jailbreak/prefill fields. These fields should be toggleable to allow the user to turn each prompt on/off as necessary from the preset sidebar.

Describe alternatives you've considered
Editing the preset to add and remove these prompts when needed, which is pretty inconvenient.

Additional context
N/A

[sceuick]

I'll look into this. The addition of JSON schemas will make this easier to implement. This feature can probably leverage a lot of that effort and might be easy to implement now.