Symbolica Setting OK as the default for the Expressions dialog

How can 'OK' be the default on the Expressions dialog. 
Currently 'Apply' is the default for the Expressions dialog.

This is by design that 'Apply' is the default for this dialog.

Starting in NX11, the Expressions dialog is a standard NX block dialog.
For NX block dialogs, the MiddleMouseButton (MB2) action will perform whatever navigation button is highlighted in blue.

Since the Expressions dialog is required to respond to MB2 actions (without OKing and exiting the dialog), the default navigation button (in blue) has to be 'Apply', so MB2 actions can be performed.

Notes
PR #7730329 
ER #9901451