When you use tags, you will want to keep them a little bit tidy. To avoid 30 variants of the same tag to get into the system, such as:
Through assigning on selected objects in the context menu, you get a clear list of available tags.
But when entering the Tags through the Properties tab of Edit Entry, you just get a free format text box.
When typing into the Tags list, give visual hints on possible tags. Similar to intellisense in Visual Studio.