After a little detective work comparing the xml files from build 28 and 45, it became apparent the the active bindings have moved from mobius.xml to the file system.xml.
I was able to copy the line from mobius.xml in build 28, as below:
<Binding name='Record' trigger='control' value='1' channel='1'/>
<Binding name='Overdub' trigger='control' value='2' channel='1'/>
<Binding name='Play' trigger='control' value='3' channel='1'/>
<Binding name='Pause' trigger='control' value='4' channel='1'/>
<Binding name='Reset' trigger='control' value='5' channel='1'/>
<Binding name='PrevTrack' trigger='control' value='6' channel='1'/>
<Binding name='NextTrack' trigger='control' value='7' channel='1'/>
to system.xml in build 45, also changing Binding name to Binding symbol, as below:
<Binding symbol="Record" trigger="control" value="1" channel="1"/>
<Binding symbol="Overdub" trigger="control" value="2" channel="1"/>
<Binding symbol="Play" trigger="control" value="3" channel="1"/>
<Binding symbol="Pause" trigger="control" value="4" channel="1"/>
<Binding symbol="Reset" trigger="control" value="5" channel="1"/>
<Binding symbol="PrevTrack" trigger="control" value="6" channel="1"/>
<Binding symbol="NextTrack" trigger="control" value="7" channel="1"/>
Now they are visible in the UI and produce the desired control, so that gets me where I need to be.
I can also right-click, choose edit and alter as required.
However, although right-clicking the fucntions etc in the tree view offers a context menu of Add, and Replace, I still can add any new rows.
regards
Chris