Torbjorn,
In nanovna-app, click the little 'camera' icon at the top of the main window. It will pop up a screenshot of the nanovna in a new window. That new window has a 'Remote" switch, toggle it on, and the screenshot will become a live update of the nanovna screen, and you can also interact with it using the mouse pointer to move markers, bring up menus, etc., as if you were touching the nanovna screen.
If your nanovna-app does not do this, you may not have a current enough version - you can the latest from DiSlord's github page.
Stan KC7XE