Over the years we've moved towards a more contained approach to rule forms using fewer and fewer pop ups and addressing specific needs based upon use case. For example, we built the rule compare feature which lists and describes the differences between two rules with the same name and ruleset.

Is there a particular reason why you need to visually compare two rules? I'm curious about the use case.

Sometimes save us doesn't work for me. There is a need for me to have two rules open at the same time to do the development, I am keeping the other rule open in a new session. Instead I am looking a feature to have them open in the same viewport.

I do not believe we have such a feature. The closest is the rule compare feature mentioned previously. If you feel strongly about adding such a feature you can work with a PCC moderator to formally submit an enhancement request. But just keep in mind there is no guarantee it will be approved.