Maybe this has been asked/proposed before, but I can't see it anywhere so, first of all, if this question is not new, just forget it.

The thing is that you can search games applying the "discounted" filter, but that shows you any discount (5%, 10%...80%)
I would really like to have the option on seeing the games according to the discounted price (for example, games under 20€ with the discount applied, even if they were more expensive before having their price reduced) , or according to the current discount (for example, games that are 50% at the moment).

Does anybody else miss this feature?

Hahahahaha yes, would have been nice and has been missed.

Ordering discounted games by their full price is one of the useless filters here.

Well, I think it's probably going to be ignored, but if somebody at Gog reads this and wants to make it real, they'd have my eternal gratitude (and some extra purchases)

We have quite good third party tools, which are quite better than built in ones, eg. this one:
GOG Deals sorted by Price
I hope it will be helpful for you :)

Definitely much better than the built-in tools, thanks

One issue with that site is that it only roughly approximates regional prices.
For the Australian region (and Australian dollar), Witcher 3 GOTY is priced at $16.08, when the GOG price is $15.79.

Given your forum location, you may have the same problem.

Greasemonkey/tampermonkey scripts can inject much of the same functionality into GOG's own website, with pricing accurate to whichever region GOG thinks you are in.

One example is: https://github.com/ghorint2t/scripts/

Keep in mind that by running the script you are injecting third party code into the GOGs website as displayed on your device. The script can see your region, and which games you own.

At the moment, the script will only run on https://gog.com/games , so authentication and payment details can't be seen by it. You will need to decide whether you trust the provider of the script to not do something nasty (or get hacked) in the future.