› The Basics
As an example, let's assume you have a Shortcuts workflow named "Get today's appointments" which fetches your appointments from the calendar, and which you only ever need when working in Notes. Here it is in the Shortcuts editor:

You want this workflow to be available in the BarCuts menu whenever the Notes app is in front. So you'll add the BarCuts Tagger anywhere to this Shortcuts workflow, and configure it accordingly:

After a few seconds, BarCuts will register and index the change, and its menu will show the workflow when Notes is the frontmost app:

And that's all there is to it!
The menu can be opened with the mouse, but you can also configure a global hotkey that will open it, in the app's Settings tab. Alternatively, you could also hook up BarCuts to Alfred, or connect it to your Raycast.