Hey folks! For the three of you who do wild things with the Godot editor, me and @gdquest have a new library (WIP) to ease your woes a bit.
Editor Interface Access is a library that enumerates ~380 editor nodes (for now), so you can access any of them with just one line of code!
@efi Godot provides access to some nodes which have functionality for plugin devs attached to them, but that's a very controlled selection. For a good reason too, you don't want to create a false sense of stability by exposing parts that might change at any moment, and you don't want to constrain contributors who'd need to change them.
However, we are interested in many key editor nodes being named sensibly, so locating them is easier (within their widget/component):
@efi Let's be honest, there are very few plugin devs and they mostly get by with tree wrangling techniques that we've been using since forever.
Though I now have a newfound perspective that approaching editor components like you would scenes in Godot, giving key parts meaningful names, etc is just a generally good idea for code quality and maintenance.
I'd push for this now, but I don't partake in engine dev anymore.
Yuri 
Efi (nap pet) 🦊💤