Sorry for the delayed reply.
In that case, adding a
Macro or Action
Macro to trigger the GO of the second Sequence in the Step of the Sequence loaded to the Main Playback would achieve what you are looking for.
To add a
Macro, you would first want to record a
Macro of just pressing the Master
button of the Master that contains Sequence 3. Then in the Sequence List for the Sequence in the Main Playback, enter the number of the
Macro that you recorded in the Step that you want to trigger the Sequence to start (scroll all of the way to the right to see the field). More information on Macros is available on
page 255 (257 in PDF) of the
Manual linked above.
To add an Action
Macro to fire a Go command for the Master that Sequence 3 is loaded on, in the Sequence List for the Sequence in the Main Playback, scroll to the right until you see the Action
Macro field for the step you wish to fire the Go command. Highlight that field and press Modify to type the Action
Macro. In this case, you are looking for Go M# (where # = the master Sequence 3 is loaded on). More information on Action Macros is available starting on
page 249 (251 in PDF) of the
Manual linked above.
In your case, I would recommend that you try an Action
Macro first. In my opinion, it is easier to execute and modify later.