In the central part of the editor, click on the block where you want to insert the page break, or create a new text block.
Position the cursor at the location where you want to insert the page break.
In the toolbar, click the 'Insert a page break' button: a dotted line appears where the cursor was positioned.
Click outside the text block: the page break is represented by a dotted line between the two paragraphs.
NB: You can remove the page break by clicking the trash can icon in the middle of the dotted line.