NM Collector Software JE (Java Edition)
Group items in a collection using folders
1. Select the Firearms folder and click Ins to create
an entry under Firearms and name it "Rifles." Do not enter any
data. Be sure to hit return after typing the new name and then
click the Save button to save it.
2. Using the same approach Create folders for "Shotguns,"
"Pistols," and whatever sub-categories you wish to group items by.

3. Add an initial item for each one by selecting the folder and
clicking the "Ins" button. You can even add sub categories using
the same method descriped above as illustrated below:

Now you can continue to create new items and/or drag and drop any
existing items to the new folders.