It's great to see you here today, @osiniavin.
You're on the right track in creating price rules on your laptop. However, this feature won't work in the mobile app. I'd suggest applying rules to your transactions via a web browser. For more information, see the Important section through this article: Set Pricing Rules in QuickBooks Online (QBO).
I can see how beneficial it is to use this feature in the app. It helps you sell products and services with pricing rules anytime and anywhere through your device. With this, I'll take note of your suggestion and submit this to our product engineers. They can evaluate your preference for future releases. I recommend visiting this website: QBO Mobile Blog. This link provides you more details about our mobile app improvements.
The supported features differ on the phone model you have. You can use the chart to easily compare them through this article: Features Availability in Mobile App.
Please know that I'm always here to help if you need anything else. Take care always, @osiniavin.