I forgot my screen time password

You have installed the Beta version of iOS 14 and I have no answer for that version however if were on other versions then my answer to your question would have been the following -

If you can't remember a restrictions passcode that you set on a previous version of iOS, or you forgot your Screen Time passcode, then you need to erase your device, then set it up as a new device to ➔ How to remove the passcode. Restoring your device from a backup won't remove your passcode.

If you have updated to 13.4 then follow these instructions ➔ If you forgot your Screen Time passcode - Apple Support

Axek F.

Follow this link

If you forgot your Screen Time passcode 

Learn how to reset your passcode if you forgot it. 

https://support.apple.com/en-us/HT211021