[EDIT]
you could achieve your goal using SDL's API
that is, unfortunately, realted with some "coding works"

Good Luck To You 

Thanks! Yes, I remember you had that app, but I am sadly on 2019 and don't intend to go back to 2017 anytime soon...

I've also been playing around with AutoHotkey to make one myself. I mean: how hard should it be to add a term pair to my termbase without any visual nonsense?

Hi Michael,

This AHK script might help you get started:

http://noradiaz.blogspot.com/2016/11/adding-terms-to-secondary-termbase.html

Michael Beijer said:

how hard should it be to add a term pair to my termbase without any visual nonsense?

That is impossible with AutoHotkey.
AutoHotkey is outsider of SDL Trados Studio, it is a secondary tool, it can not do any kind of elegant work.

Michael Beijer said:

how hard should it be to add a term pair to my termbase without any visual nonsense?

That is impossible with AutoHotkey.
AutoHotkey is outsider of SDL Trados Studio, it is a secondary tool, it can not do any kind of elegant work.

so, If you want to make a primary tool, use C# (SDL's API)
SDL Trados Studio itself and SDL Trados Studios's PlugIns are all made with C#
AutoHotkey is.. a toy.

I can hardly manage AutoHotkey, so no C# I'm afraid. ;-)