The Tag Manager is a powerfull tool permitting to edit metadata information of selected images. 
It consist on two pages: Keywords and Advanced Metadata Editor.

The "Keywords" page is for fast keywords management. It contains a generic list
of categories that can be costumized as you like.
The "New Keyword" button adds a new keyword to the list;
The "Remove Keywords" button removes all checked keywords from selected images;
The "Clear Keywords" removes all keywords from selected images.
To add keywords, check any keyword from list and click "Apply Tags".
Keep in mind that to write image metadata the "write iptc metadata" option
on GTKRawGallery preferences has to be checked, otherwise keywords will be stored
only into the Sqlite database for fast search. That can be the right choice
for users not interested to keywords portability.

The "Advanced Metadata Editor" was designed thinking to advanced users
and permits to edit a huge list of metadata. Exif, Iptc and several Xmp groups are supported.
To build a list of tags:
1) Select a group;
2) Select a tag;
3) Click "Add";
Repeate again to add new tags.
Finally click "Apply Tags" to write metadata.
Unlike keyword tagging, metadata is always written!
To avoid rebuilding the same tag list, you can save it as a template to quickly reloading later.
