Allow unsorting columns from contextual menu in column header

Currently, I can only select “Unsorted” from the application menu. Although the column headers offer sorting options in the contextual menu, the “Unsorted” option is missing.

This seems like an oversight. It would be so useful if I could on the fly, using the contextual menu choose Unsorted. Please refer to the screenshots below for a better understanding of this inconsistency in DEVONthink Pro:

Noted but bear in mind, this is DEVONthink 2.x, which is now in maintenance mode, i.e., only receiving critical bugfixes.

The menu of the columns header can be used to customize the columns, not to switch the sorting.