I started this topic:
The question was closed, because the first version was a bit unspecific. I updated it and waited for being reopened. Nothing happened. The FAQ doesn't give any hint how to handle this.
So I just posted a similar question, because the FAQ doesn't offer a real solution for getting an edited question reopened again:
I know, that wasn't the best solution, but there was no real alternative proposed and the topic seems being to special to gather a high interest.
So I'm being downvoted and closed again. I think, this is a rude an unfair style, as I've been trying to be as specific as possible. And it's a clearly formulated question now, which can be answered in the way "XYZ provides a way to work with multiple-users on the same cashbook from different machines".