To answer my own question:

Raymarine just sent me a reply and informs me that the ST600R only
adjusts/operates the drive when it is in the AUTO mode..

This is surprising since the ST5000 control unit will allow control over the
drive in STANDBY as well as AUTO mode.

Additionally my back up control, AH3000 contro and Remote allows this
control in both mode

I guess I will have to live with this. In my experience with my old AH3000 I
often sat in the shelter of the dodger and steered the boat with the
Handheld Remote (while in STANDBY).


--
My experience and opinion, FWIW
--
Steve
s/v Good Intentions