I am having the same issue with creating custom moods. I have tried this both way, selecting the sounds I would like to mix together, select the enigmatic silence button, then the plus to save the custom mood. I stop all the sound with the bottom square button, then select the custom mood I created in column two to test the mix and nothing. I have retried this with the above order as well and I am striking out. Could really use some help.
Thanks.