Unicode Character Input

Can't teach her Alt+Tilde? (er, Alt-Backtick really)

On Linux you can use the Compose key for this. It is also possible to define custom sequences.

I use it quite often to type in unicode characters like ⌘, or music sharp/flats, etc.

You seem to be trying to solve a problem that could easily be solved by using a Compose key: https://en.wikipedia.org/wiki/Compose_key

I do not want to learn new input methods for every program, I want a standardized compose-like functionality that allow me to write both diacritics and backticks ( a plus for the rest of unicode)

i regularly use Compose for unicode symbols, mostly stuff like ←↑↓→–≠ . it's not too clunky, for example "→" is "RAlt, -, >" in succession.

You could look into using "compose key." It's quite intuitive and opens up a whole new world of expression.

How are those Unicode characters typed in an editor with a normal keyboard?

If you're on Linux, you can set up your compose key map to do the job. here's an example: https://gist.github.com/carlobaldassi/8951743

It would be nice if the suggestions included the keyboard shortcut for inserting that character.