You can Right Mouse Click on internal nodes, leaves and outside the tree to see multiple options adapted to your selection.
The 'History' button on the left side permits you to see the changes you have made and eventually to go back.
You can Press 'Shift' Key + Left Mouse Click on the leaf's node to access to a gene card in a new window.
You can Press 'Ctrl' Key + Left Mouse Click on nodes to do a multiple selection.