There is a checkBox now in the tree view to finish activities without opening the edit screen. With "configure outline" you can show it or hide it.
You can add a blank border to the buttons in the tree view if it is difficult for you to hit the buttons. This is done in the new settings menu in the list of outlines. Thank you to Bernhard for the hint.
The context menus have titles now showing the element you are working on.
New Beta Version of the Android Outliner.
There is a CSV import/export now and a todo-view which groups unfinished activities by the due date.
Attention! This version wipes all your outlines and creates new test data!
From now on your data should survive new versions. You can use the import/export functionality to backup your outlines to the SD-card.