The Nova landing page on nova.app mentions a toolbar:
You can easily create build and run tasks for your projects. We didn’t have them in Coda, but boy do we have them now. They’re custom scripts that can be triggered at any time by toolbar buttons or keyboard shortcuts.
Where does this toolbar reside and how can I populate it?
Apparently, “toolbar” in the context of Nova is quite different from a macOS toolbar and refers to build/run/clean tasks only:
I was rather looking for a way to define a customizable toolbar other apps such as mail.app etc feature, aka a way to assign commands which are multiple clicks away to a customizable toolbar.
Sure, I can and do define keyboard shortcuts, but for some activities, I prefer a more visual approach rather than having to memorize a gazillion keyboard shortcuts or browse through the command palette.
Maybe a feature for a future release?
We do currently have a feature request out for an extension API to add toolbar items (top of window) and / or status view (bottom of editor) items. I’ll add your vote!