Let's say you've got a chair and a cushion in your inventory. You want your sales team easily see the related tablecloth whenever they add a table to an order.
When editing your chair, you can click into the 'Relations' tab
From here, you can click 'Accessories' and search your inventory for your cushion.
Once you've added all the different cushions or tools you'd like added you can select if these accessories are 'Required', if you want them 'Auto-Hidden' on your projects, if the accessories are to be 'Nested' with the main item, and how many will be suggested.
Once you're done entering in these Accessories click 'Save and Close' at the bottom.
Now when you add this chair to a project, you will see the related items next to the item's name.
As you can imagine, this can be used for a wide variety of use cases: Amps and extension chords, chairs and chair covers, props and uplighting, and so on.