Is your feature request related to a problem? Please describe.
Custom Trigger activation should be a UI feature with checkboxes, I too began using WA properly a couple of weeks ago and this made such confusion it was all triggers or any triggers, only found the solution by joining discord and asked there is even a bot comand and since I joined couple days ago I see this being asked all the time.

Describe the solution you'd like
Check boxes on individual triggers for trigger activation.

Describe alternatives you've considered
The backend already supports it since we can use a custom trigger activation code, Its just a UI thing and I feel this would help so much new ppl starting making their own auras.

Additional context
TLDR: https://github.com/WeakAuras/WeakAuras2/wiki/Aura-Activation-and-Deactivation#custom this but in the UI :D

Duplicate-ish (to paraphrase ongrimmar) of #1236