I entered an idea. Than I saw Vadim's idea and realised that my idea was furtrher development of his. So, I wished to delete my ideas and re-enter is as a modification of the Vadim's idea. I wasn't able to do so however as there is no "delete" button.
Add "Delete" button for ideas.
Make it possible to shift ideas from one root to another, if possible. For instance, if you discover that your idea is not completely new, but a modernisation of an idea submitted earlier, one should be able to more his or her idea to the right location in the idea tree without deleting and re-entering it.