I am not sure what is going on on your system. I guess you are using i-doit 1.9 open or 1.9.1 pro? Do have a mapping between an LDAP group and an person group in i-doit? Or do you use the "Standard LDAP group" in your system settings?
There is a little feature within the Admin Center that let you install add-ons via CLI. On a shell change to the installation directory of i-doit, for example "/var/www/html". There is a sub-directory called "admin" with a file called "index.php". With the following command it gives you a short help:
Welcome to our i-doit forums. If you use the CSV data import the only way to set "static values" will be within the CSV file. For example, add another column for the CMDB status and insert the value "ordered" for each object in a row.
Linux Mint 18.1 is based on Ubuntu 16.04 which is currently not supported because of PHP 7. Please switch to another GNU/Linux distribution or just wait for i-doit 1.9. The pro version will be published in May.
in the Open version it's not possible to change the objecttype groups within the GUI.
In the Pro version you have a tool called Quick Configuration Wizard that allows you to edit them.
What you can do is edit the database. The list of groups is in table "isys_obj_type_group". Just add your own group there (ID above 1000) and make sure all columns are filled (Just make it match the existing ones).
Add the LC (Language constant) you created to a custom language file. An example can be found at /src/lang/de_custom.example.inc.php. More information here: Knowledgebase