On iOS (iPhone):

You can duplicate and delete mind maps while you're in the dashboard as well as from within the mind map editor. 

To duplicate or delete a map from the dashboard, simply long-tap onto a map thumbnail until the menu appears, then select the desired option from the list.

To duplicate or delete a map from within the map editor:

1) Tap on the Map Actions button in the top-right corner of the screen.

2) In the Map Actions, tap on More (the three blue dots in the top-left corner of the screen).

3) Select the desired option from the menu.

On Android:

You can duplicate and delete mind maps while you're in the dashboard as well as from within the mind map editor. 

To duplicate or delete a map from the dashboard, simply long-tap onto a map thumbnail until the context menu appears, then select the desired option from the list.

To duplicate or delete a map from within the map editor:

1) Tap on the Map Actions button in the top-right corner of the screen.

2) In the Map Actions, select the desired option.