On the LifeSpace mobile app, you can swipe left on most items to delete. You will see a trash can icon appear if you have the rights to delete the item.
On the LifeSpace desktop app, right click on the item you want to delete.
LifeSpace "Archives" spaces rather than deleting them right away. This allows for deleted spaces to be restored if done by mistake and also addresses the issue of shared spaces that might not be of interest to you any longer but is still used by other users.
Archived spaces will have the option to be purged from the cloud in a future release (targeted for September 2019).
Note: Deletion of Bookmarks, Checklists, Tasks and Notes do not archive. They are instantly deleted from your device and will be deleted on all other devices upon the next sync (generally within 2-3 minutes)