This question (How to get values after an equal sign) is basically what I want:

Given a line of text, with named parameter looking syntax like color=red, using bash how can you grab that color value (yielding red)?

Except in that question, the line of text is entirely those key-value pairs, so the accepted answer utilizes bash's eval since that syntax happens fit very nicely.

I'm wondering for a generic line of text like ⎜ ↳ Synaptics TM3289-021 id=13 ] how I could grab that id value (yielding 13)?

Maybe utilizing regex, where I know the line will contain [whitespace]id=<TEXT I WANT>[whitespace]?