If you have recently inserted a topic in a group, you can use 'undo'; it will reverse the last change (ignore, merge, etc) that you did and you can apply it several times to reverse several steps. If you need to remove a topic from a group, and 'undo' is not a good option there is another way, and it is easy to perform if you follow these steps:

  1. Create a new group.
  2. Click the 'merge' iconsave image
  3. Now click the 'drop' icon on the newly created group:save image
  4. Your topic will now drop into the newly created group and leave the former group.
  5. Click explore. Once the exploration is finished your topic will be outside the group.