If you would like to update multiple entires in one operation, the batch actions is your friend. By selecting one or more records, the Actions button will appear. By clicking the button or activate the context menu with right-click, you can perform different actions to the selected records, such as "make observations", "add or remove tags", "changes status" etc.
Here is an example of adding a new tag "To be removed" to 4 records.
Note: If you would like to update more records than are listed on a page, you need to navigate to the next pages and select all entries on each page.