If there are errors in the project the Modeler prevents deployment. It may be the case that the errors are all in one document that is not even being used yet. In version 3, you can now exclude the document. This means that it is not checked for errors and not deployed. It is as if the document does not exist. Indeed, usages of the document result in errors.
You can exclude a document by right-clicking in the project explorer and choosing ‘Exclude from project’. The name of the document will be put into parentheses and the icon will be grayed out. To quickly find all excluded documents you can use Find Advanced (Ctrl+Shift+F).
A funny use for this feature is to draw high-level “processes” in microflows. These fake microflows will, of course, contain many errors but by excluding them you can still deploy!