Hi,
the said button is available in the result screen only. So you must select something (no matter what) before to get the result screen, for instance:
type=transaction
transaction code=SU53 (or anything else)
remove the x from 'only with changed SU22 data' and set it for 'display appl. with identical su22/su24 data'.
then you will get a resutl screen for SU53.
The #set 2a status' button i son the very right in the button line on the top of the screen.
good luck.
Bernhard