I will definitely add the option to rebuild the library, as I plan to remove support for all HB rules, including 1.40, in the new version of HD. In the new version of HD, you will be able to continue playing games from 1.38+ versions, but you will not be able to continue games from 1.40. Games from 1.40 can still be continued on the old HD, but I will likely disable access to the lobby from the old HD version either immediately after the new version is released or after a short period.