To edit multiple products that have the same characteristics (for example: price, tags, etc.) you need to go to the Configuration menu - Products and select the products you wish to edit (in the box on the left of the product)
After you have selected the products you want to edit, click on the Bulk editing button.
A new window will open where you can make the following changes:
Change price - the price you will add here will apply to all the selected products
Change Category - move the products to a category you select here
Change VAT - change the VAT for the selected products
Change Tag - add a tag or modify the tags of the selected products
Add to existing tags - this option allows you to add a new tag to your selected products and keep the existing tags