We'll create fresh WordPress site with Smart Tag Insert installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Once you have defined a list of tags, this plugin will add a box in the post editing page through which look for relevant tags basing on the post content. The most relevant will automatically be selected (although the selection can be changed), and selected tags can be added to the post with a click.
It is also possible to use the plugin to reassign all blog’s posts tags through a handy posts tags rebuilder.