There is no built-in functionality to import an asset group list. I think it would be easier to build a SQL report under Reports\Create New Report, rather than create a group. You can easily insert a list of asset names into a report. Open the report builder under Reports\Create New Report and add the following to the Criteria column of the tblAssets.Assetname expression, inserting your own asset names into the syntax:
In ('name asset 1','name asset 2', 'name asset 3')