Change Prices on site

Hi,

Variants are not linked to categories directly. Only the main products are.
So, the moment you add a filter on a category, you're only targeting main products.
Also, price.price_value*2.00 will multiply the price by 2 not add 2%. If you want to add 2% you should rather use price.price_value*1.02

Hi,

Yes, an action will be easier.
Go to the products listing in your backend. Click on the category on the left explorer.
Set the filters on the top right corner to all sub categories, and to display only variants.
Then, increase the number of elements per page.
Then, use the global checkbox to select all the variants on the page, and click on the actions button.
In the popup set the action to update the price and it will do what you want.
Then, reproduce for each page. With 500 elements per page, it should be quick.

Also, you could create a mass action and enable its "actions as a button" so that would add a button to run the actions of the mass action on the selected elements. That way, you don't have to reconfigure the action for each page and you can potentially reuse the button in the future.