Reference sets are used to represent the component parts with simplified geometry/different state of the geometry with the options to filter and control the display of a component or subassembly part in higher level assemblies.
With enhanced 'Reference Sets' helps to easily determine the content of your existing reference sets by looking in the Reference Sets folder.
You need to enable the 'Display Reference Sets Folder' option in the customer defaults settings.
In 'Reference Sets' dialog, the System-defined reference sets (Model, Empty, and Entire Part) are presented at the top of the list and user defined reference sets are presented in alphanumeric order whenever they are created.
Same order is displayed when you use 'Replace Reference Set' in the assembly.
'Reference Sets' node is available in the part navigator when 'Timestamp Order' is on or off with the difference as mentioned below.
Reference sets Folder - Timestamp Order is On
When Timestamp Order is on, the Reference Sets folder displays only the reference sets and their first-level children, such as solid bodies, curves, or sketches.
Reference sets Folder - Timestamp Order is Off
When Timestamp Order is off, the childrens will show their construction details, such as Features, Curves and Dimensions, External Reference, Reference.