Is it possible to change the document type when creating new documents with drag and drop within Mozilla browser? Even setting the preference "Create and Edit -> Document Create Default Type" seems only to affect "Action -> New...". Currently we have PDMLink 10.2 M030 CPS04 installed.
For the main Document "object" that gets created...no. You can't change an object type definition of anything once it's created. You can of course change the attached file, and if you have added some dropdown-list attribute to show the document type as Report, Test, etc...you can of course change that. But not the fundamental object type itself, since that is too encoded into the system with the Object Initialization Rule, Lifecycle Templates, etc...if the wrong document object type was chosen at creation your only option is to fully delete it and start from scratch.
If you want to be able to select the document type from a drop-down menu, you must use Actions > New > New Document or Actions > New > New Multiple Documents.
Both action windows support the drag-and-drop functionality.
But, if you're specifically talking about using the drag-and-drop feature from the Folder Contents table:
I tested this using Mozilla on a Windchill 10.2M030_CPS15 server -- so if the Document Create Default Type preference isn't working for you, it might be a bug that has since been fixed. (I wasn't clear on whether the preference wasn't working at all for you, or if you were just emphasizing that setting the preference to com.ptc.core.foundation.type.common.commonResource:SELECT_A_TYPE doesn't apply the Folder Contents drag-and-drop)