You can create your own custom groups for local (flex) items to help find them easily and isolate reporting (you cannot create groups for HQ (core) items.
From the Product Listing, choose the Custom Groups tab:
To create a new custom group:
1- Click the + to create a new title for the groups
2- Then type in the name
3- Click checkmark
4- Click the + to add the groups under the title you created
5- Then click the blue + to expand
6- Enter the name
7- Repeat as needed
8- SAVE when finished
Then you can apply the custom group to your items under the item detail screen and save:
NOTE: you can only apply custom groups to Flex items.