For trending and extraction of data in the openHistorian 2.0, you can use the built-in web tool that is designed to plot data and export to COMTRADE or CSV. You can use the following URL to reach it, though you will have to replace "historian-server" with the hostname of the server that the openHistorian is installed on.
From there, you will need to select data points on the
Select Points tab. Select your time range by switching to either the
Trend Data tab or
Export Data tab for trending or data extraction respectively.