When inspecting an object inspector provides two options on how to sort and group the slots. By default it lists all the slots alphabetically. The other option is to list them in the way they are defined. It can also group the slots by the direct class they’re defined in. Slots can be sorted or unsorted when you grouped by classes as well.
Inspector provides two check-boxes to change the ordering at run-time

 Group slots by inheritance [X]
 Sort slots alphabetically  [ ]

The default values of those can be set in ~/.swank.lisp

*inspector-slots-default-order* to either :unsorted or :sorted. (:sorted by default)
and
*inspector-slots-default-grouping* to :all or :inheritance. (:all by default)

I set *inspector-slots-default-order* to :unsorted, and then it shows all the slots in the order they’re defined in the source code (implementation or MOP can reorder them, but that usually doesn’t happen).