- How can i combine two rooms (not grouping)?
Based on what you stated before editting/cleaning up your post. you’re wanting to add a speaker to an existing room to create an stereo pair?
https://support.sonos.com/s/article/1066?language=en_US
- Why is it not possible to autoplay in different rooms?
According to support document, you can. It does not clarify exactly how, but I would guess that you need to create a saved group that you can then select in autoplay.
https://support.sonos.com/s/article/4838?language=en_US
- Why does the sonos app create a new room Dining Room 2 when i wanted to add a new product to my Dining Room?
It’s just a step in the process.
- Why does the sonos macOS app have less options to adjust your current system (makes absolutely no sense to me)
Because Sonos realized a few years back that very few people managed configurations with macOS (or Windows), primarily using iOS and android. Therefore, they diverted Dev resources to features that customers were using with higher frequency.