I'd suggest putting them on the surpression list as they are also shown in situations where you might not need or want a on-click action.
When creating a new app with the Blank app template, you will always have at least 8 such warnings from the Atlas_Core module.
In recent versions of Studio Pro, you can suppress warnings from the Marketplace modules. To do that, in your Errors window, click the Suppression Rules button and check the Suppress warnings from Marketplace modules option.
For unused microflows, I suggest excluding them from the Project, at least until you decide what to do with them. For microflows that are called by name by some Java Actions, you can manually mark them as used. In the Properties window for the microflow, choose Yes for the option Mark as used.