@Spass1966 The Software Center has been unmaintained for a while now. We removed it because of that and because it had been the focal point of any review that came through pointing out how it "didn't work" and "how it wasn't showing any software (debs)", so instead of having to explain over that it was in development we removed until it was more feature-rich. Also, because its interface was made with Plasma UI components and with MauiKit being developed, it didn't make sense not to redesign it. There's an open issue about it Nitrux/nx-software-center#62.
We did mention why we removed the Maui apps from the ISO. They weren't working with Qt 5.12 at the time and, like with the SC, we preferred not to include them until they function once again instead. We do include Pix currently; Index has had features added, VVave needs some fixes too, Nota and Station required fixes also because of the changes in MauiKit. There are other applications, but they are only available as source code for now.