Please add a "Activate another product" button or something like that on the product activation page if we want to activate MORE THAN 1 CODE.

I have 3 activation codes. I enter one and I need to manually go to the page with the activation of another code again, and so on 3 times. And if you have 5 codes, then 5 times. And if it's 10, then 10 times! Why can't you add a "Back" button, or "Activate more"? Is it really very difficult?

This would be a huge life saver. Even Steam doesn't have this feature.

Not really, you can activate multiple steam keys at once. See pic;)

That's interesting. Here is a pic of what I see on my steam registerkey page (https://store.steampowered.com/account/registerkey).

How did you get that button?

Only one key at a time in Germany.

My bad, looks like it's a feature from add-on, Augmented Steam to be precise.