I’m not much of a notion user, but I just pulled it up, and surprisingly, they override ⌘-n for new page.
They also have / commands, so if you’re in a notion page, you type /page Enter, this creates a new page too. This reminds me of the command palette dialog that a lot of apps have (like VSCode, SublimeText, etc) where you hit ⌘-P (or something), then you can type a command. I know you have mentioned that before @pirijan so maybe something to consider.
This would also make it easier to extend. Other things I’d like keyboard shortcuts for are opening up my favorite spaces, Explore, and maybe the global notifications dialog. 