Select the ids of the trees to be cut: choose the ids in the left side list and move them into the right side list. When your choice is made, press Ok.
Selection of the trees
To select a tree in the list, click on its identifier.
Then possibly:
click on another id while pressing the Shift key to select a block of contiguous ids
click other individuals in the list while holding the Control key to select trees which ids are not contiguous
Move from one list to the other
Add the left side selected trees to the right side list
Remove the selected trees from the right side list