Currently this can be achieved by opening your profile ini file in %APPDATA%\OBS\profiles and changing the desired hotkey value to 9.
If by any chance you're having trouble with other keys, check this out
http://msdn.microsoft.com/en-us/library/ms927178.aspx (remember, the values in that page are in hex while OBS wants decimals, so unless you can convert numeral bases, you'll have to open up that good old calculator).
I doubt that there is any real benefit in implementing a system wide keypress lockdown just to capture tab key (unless there's already something like that in place).