I don't want to participate in promotional activities, how should I set it up?

The checkbox used to be under "Settings" but it's gone now. Possibly because they have a problem with anyone who doesn't want to sell their models at 50% off. I would send a message to support@cgtrader.com and ensure that they know that you don't want to participate.

I still can see that option in my sales page. The layout and some settings has changed, but you should be able to opt out from all promotional campaigns and discount programs. https://www.cgtrader.com/profile/sales#discounts

I also see that they changed some things. But when I open all the models in the public profile even though the icons are turned off in the settings for the all discount programs it still shows 50% for most of the models

they have set the discounts so that the most convenient discounts cannot be set to a minimum of 30% but at least 50% and there are some sales options on other sites that however for now have a bug and cannot be set ... they have already been informed and I think they will fix it in the next few days