Hey Adam thank you for posting in the Lucid community! Our sincere apologies for the delayed response on this thread - I wanted to follow up in case this answer may still be useful to you and to provide a solution for other users who see this thread in the future.

To evenly distribute additional outer bubbles/additional idea's to your mind map select the center idea and using your keyboard hit "tab". This will add an additional sub idea directly linked to the parent in the center. Once you have added your desired amount of sub ideas select the "Auto Layout" option located at the top of your document. The auto layout feature will re-organize your sub-set of ideas in a even manor around their parent.

Here's a quick GIF showing the process!