Hey hwuyule if you are looking to insert stuff into the sketch UI its super helpful to learn about AppKit. Things like NSStackView
, constraints, and view controllers are all needed.
https://sketchplugins.com/d/2221-sidebar-error-in-sketch-v70
If you are just looking to open a NSPanel on top of sketch at that location you'll still need a bit of AppKit knowledge for where to position the panel. Happy to help you figure things out if you are still interested. Unfortunately, there's no javascript only way to do what you are trying to do.