The Experimental DLC is a special DLC that serves as a temporary place for new features to be experimented and tested before they would make their way to an official DLC.
True to its name, experimental features that do not make it during the test period due to gameplay balance issues or simply lack of fun will eventually be dropped.
The Experimental DLC is freely accessible to users who have purchased all of the 4 existing DLCs (Subsidiary DLC, City Economic Simulation DLC, Digital Age DLC and Banking and Finance DLC.)
Visit the Capitalism Lab official web site for more details about Experimental DLC: https://www.capitalismlab.com/experimental-dlc/