What I mean is similar to the work done in this package for Atom. This is essential, since the workflow is often based on using hotkeys, and this title bar keeps appearing whenever one presses Alt (Windows).
Update: this request was originally directed at the Windows version, however there are people who would like to see this same change on macOS, so I changed the title to a more general one.
I wouldn’t mind it being gone in macOS as well. In Atom the title bar can be removed/integrated, as you can see here.
Th extension CustomizeUI for the code editor VS Code—as well an Electron app—does the same thing and the additional OS window manipulation options are shown on hover. Discord must be doing something differently then.
I would also prefer a titlebar-less window mode with the “traffic lights” icons on macOS being integrated into the sidebar. 
Chiming in to say I’d like this as well. As other’s have said, it’s been done in other electron apps, so it does at least seem to be technically possible.