The Mass Edit Terms screen allows you to quickly add or remove taxonomy terms from any content in WordPress.
The first step is to choose which taxonomy you want to modify. At the top of the screen, use the dropdown boxes to choose your taxonomy. In the image below, I’m editing “Posts” and the “Tags” taxonomy.
In the main part of the screen, you will now see all your Posts and the Tags attached to them.
To add Tags to any Post, simply start typing in the box in the right column. In the image below, you’ll see that TaxoPress is suggesting Tags based on the characters I am typing.
To remove Tags from any Post, simply place your cursor into the box in the right sidebar and click “Delete”.