Yes, you can segment your visitors by experiment they have participated in, and even segment your visitors by each specific variation they got to see. This lets you get more insights into how t different variations have affected your other reports in Matomo (Piwik).
Say you are running an experiment “Buy Now Button Color”. You can segment Matomo (Piwik) reports by visitors that have seen the “Blue color” of the “Buy Now Button Color” and compare the report to the visitors that have seen the “Red color”. This lets you compare in detail how each variation has performed against each other.
By using the segmentation in combination and viewing the Visitor Log, you can see in detail the path and actions of each of your users who viewed a particular variation. This lets you view how the behavior of a particular user may change depending on which variations they got to see.