You're misunderstanding the suggestion or I'm not being clear enough.
Currently the green (I think) button activates the 'Guide' button on the remote STB.
However, to exit from the guide there is no button in the WD remote that is mapped. Instead you have to press the blue button to bring up the on screen controls and navigate to the 'Back' button to activate the 'Exit' button on the remote STB.
I'm proposing that the 'Back' button on the WD remote should activate the 'Exit' button on the remote STB directly, without having to use the blue key at all to bring up the on screen controls.
Current the 'Back' button on the WD remote does nothing when inside the Slingplayer
So I have looked into this some more, with a great deal of help from Alan Richey, and it seems there may be a bug with the WDTV player.
It turns out that the 'Back' button on the WDTV remote works correctly in controlling the "Back up" function on my Sky+ HD box, but will not control the "Exit" function on my IPTV.
I initially assumed it was just something missing in the custom remote that Alan had kindly made for the IPTV but it turns out that it's not that simple (how could I ever doubt the legendary Al Richey?)
Using the glorious RemoteMaster software we tried all the common button-to-function mappings on the IPTV custom remote that ought to have caused the WDTV "Back" button to work and indeed at one point I did a test and made all the buttons on the custom remote map to the 'exit' function on the IPTV. The result was that all of the physical keys on the WDTV remote that the WDTV Slingplayer maps produced the 'exit' function....except the 'Back' key which still did nothing.
I then installed Alan's custom Sky+ HD remote onto my Sky Slingbox, without changing the function mappings of any of the buttons, and this also then caused the WDTV "Back" key to stop working.
So this all suggests to me that the "Back" key stops functioning when a custom remote is installed....but only with the WDTV Slingplayer; note that both of the above-mentioned custom remotes work fine with a SlingCatcher, i.e. the SlingCatcher's physical 'Back' button works correctly in both cases.
I'm hoping the above will make sense to someone in the technical department @ Sling and what is probably a simple fix can be made so that the physical "Back" key on the WDTV remote works in all cases that the physical "Back" key on the Slingcatcher remote does.