If i select sort order "Name" then go between folders, it shows "Name" as sort order which is correct.
If for one folder i manually drag thumbnails in different order, then it shows Custom sorting order which is also correct, however after switching to another folder where i did not apply any custom order, XnView MP still showing Custom sorting order.
Perhaps to avoid confusion it should only show Custom if currently open folder contains .XnViewSort file?

Same behavior with Filter.