Can't find GUI declaration in Camunda Modeler source-code

I was searching through the Modeler Github source-code and didn’t find any GUI elements or code. If you could tell me the folder that contains the information related to the GUI, I would greatly appreciate it.

Are you looking for source code to expand modeler? If so here is the link.

Not at all. I want to edit the source-code of the Modeler, not expand on it. Basically, I want to edit some visual properties of the GUI, but how? I know that a plugin won’t be able to modify the vanilla GUI elements, like the colour of the menubar.

Are you looking for this? https://github.com/camunda/camunda-modeler/

Note that this project only contains the general application. The BPMN & DMN Editors + Properties Panels are integrated via bpmn-io.