When pressing by mistake closing map or layers there is no undo.

[SOTIRIOSTRIANTOS]

When pressing by mistake closing map there is no undo. You have to close project without saving it and reload it.  

[AubriKinghorn]

Hi! 

You can re-open any map in the project by going to the Catalog Pane, expanding the Map heading and double clicking the map. Then you don't have to close and reopen the project.

Cheers,

Aubri