It depends on which of the two Modelers you’re using.
And then Click ‘Delete’ in the Properties pane.
In the Modeler, go to the Project Explorer on the left hand side of the screen, right mouse click on the unwanted page (or microflow or any other item) and you’ll see delete as one of the options in the popup menu. See the screen shot below:
if you right mouse on page RFQ_NewEdit, for instance, you’ll get a popup menu with delete as one of the options.