Presently Configurations are displayed in the Test Run creation pane ("Start new test run") or edit pane ("Edit run"), in the order the Configuration Groups were created. And within each Configuration, the individual items are also listed in the order they were created.
From the POV of the create/edit pane, this can disrupt the flow, where dissimilar items can end up proximal to one another, and similar items can end up distal to one another.
From the POV of selecting a choice within a given Configuration Group, this can result in divergent ordering over time. Or there might be a preference to place the most recent items (eg, latest product versions) at the top of the list.
Workarounds:
Delete as many items from a Collection Group as is needed, then add them back in the desired order.
Likewise, the reordering of collections would require the deletion of as many collections as necessary, then recreate them (and the items belonging to the collection) in the desired order.