New UX: Warning before leaving a page that has unpublished edits

[David_Elston]

In classic, when I make changes to a dashboard and try to close the page, I am given a choice whether to discard or save the changes.  Perfect.  

In New UX, i have lost major edits without realizing it by clicking an action, my page gets changed to where the action points.  Then my edits are left unpublished and therefore erased.  Not good.

Please add a warning to a model builder that tries to leave page with unpublished edits