Static discount option

Hello, is there any way, how to set static discount -10? There is written:

Set a new price using a number (eg. 49) or percentage (eg. 90% of original price)

Of course i am able make discount -10$ also with percentage calculation or with new fixed price. But what in case i will change a base price of additional product? In this case i have to edit all products where is defined as “Bought Together” and set new fixed price or percetage discount…. Or is there at least any posibility how to set it in bulk?