Not a big deal but, when I create a new "Host Group" ("Puppet Group" menu item in the settings), if I immediatelly try to add parameters I get an error. Example:

2 errors prohibited this hostgroup from being saved
There were problems with the following fields:
    * Group parameters is invalid
    * Group parameters is invalid

Workaround: First create the group without any parameters and click CREATE. Then re-open it for editing and only then add/create the parameters.