To keep a better overview, i would like to group various sites by a topic.
I have some basic sites, and a lot of event based sites. The dropdown at the top right and the dashboard is getting more confusing the more websites you have. I would appreciate, if i could specify some topics, and assign each website to a topic. These topics are shown on the dashboard and in the top right website dropdown for a better overview.
see the feature request: Show Websites by Group in 'All websites' dashboard · Issue #2174 · matomo-org/matomo · GitHub
Thanks a lot! When this is going to be released? Or is there a chance to vote for this feature request?
you can comment there to say +1 
otherwise sponsor us to work on it is possible, via http://piwik.org/consulting/
We’ve just released a new plugin which could really helpful to you: Roll-Up Reporting aggregates data from multiple websites, mobile apps and shops into a Roll-Up site to gain new insights and save time.
Roll-Up ReportingRoll-Up Reporting lets you aggregate data from multiple websites and apps into one single site. It lets you answer questions like “How many visits happened on all of my websites and apps?” and “Which campaigns contributed the most across several of my websites?” or “How do my various Brands overall compare with each other?” When you have several shops (eg white-labels) it is very valuable to see how your ecommerce shops are performing overall. Or when you are a web agency and you are serving many customers and want to provide each customer with a single aggregate view of all their web properties. Roll-Up Reporting lets you analyze this aggregated data in one site so easily. It saves you lots of time and helps you gain the insights you need instantly.
The Roll-Up Reporting User Guide and the
Roll-Up Reporting FAQ cover how to get the most out of this plugin.
For any other question feel free to contact us.