I've just updated to V4.6.6 on my Shield. In Settings/General/Remote Shortcuts I previously used Blue(F1) for Schedule but that option is now missing from the dropdown list. I can force the setting on the client from the Server side, but it still doesn't work.
Hitting Blue(F1) when defined from the server as schedule (and showing as such but greyed out in the menu) just goes to the settings menu.
That in itself might be useful as I have been after a direct route to Settings, but it seems like a bug.
EDIT Operator Error - Ignore!!
The Schedule option wasn't selected in the Manage Navigation part of settings. Once ticked Schedule appears in the dropdown and all works well again.