How to bulk edit WooCommerce sale prices to 20% below regular?

First way:

• This way is good when you can do it for some products or variations on the same one page in the Products Editor
• Select some products
• Enable 'binded editing' switcher
• Hover on any selected product sell price cell and click on calculator icon
• In calculator select: rp- and in the text field there enter 20, and in the last drop-down select percents
• Select prices rounding if you need it
• Click on blue accept button on the calculator and wait until this bulk operation is finished
• If you did smth wrong you can roll back this operation in the tab History

Second way:

• In this way you can apply changes to all products on the site or to the filtered ones by your logic
• So make products filtering by category or categories, or/and any other parameters if you need it
• Go to tab Bulk Edit and select field 'Sale price' there
• Enter 20 in the textinput
• In the drop-down select 'regular price minus %'
• Click on 'Do Bulk Edit' button and wait until operation is finished