Option to add characters to special character list

[yashamon]

At the moment newline character is a special character that is accessed by enter key. That's nice but it would be good to add other characters to a list of special characters accessed this way. For example the characters $, {, [ are a pain to enter manually. A concrete example jump to M inside latex code:
blah $M$ blah

If we add $ to special character list, we can just do M enter.

[ggandor]

I guess something like Leap's equivalence classes is what you're looking for, we should just port that. I cannot promise anything for the near future, but a PR is welcome from anyone.