Adding Blitzes to Custom Defensive Playbook

I have been trying to add the in game blitzes like 4-3 Nails to my custom playbook but it is always rejected as invalid. I have tried the obvious D43,43B Nails,1 but it rejects it. I tried a bunch of other combinations but none of them worked. When I look at the Plays.xml file it appears as if the blitz plays are a lot different in how they are set up from the standard defenses. Is there something specific I need to do to add them to my playbook?
I am trying to achieve what the game suggests in the pop up help on the play calling setup screen where it mentions that if you set the blitz weight to 0 it will use the blitzes in your playbook.... but I can't add any to my playbook.
One reason I am trying to do this is because I play out most of my games but I Sim some of them. I have noticed that when I Sim it will use more blitzes and varied ones. When I play out the games there no blitzes suggested and I have to search through the blitzes to call one instead of looking in my custom playbook. I would love it if I could add blitzes to my custom playbook and give them weight so they will be suggested while playing the game out. Then if I need to I can also just search my playbook for the ones I want to call. Hope all of that makes sense...
I am trying to achieve what the game suggests in the pop up help on the play calling setup screen where it mentions that if you set the blitz weight to 0 it will use the blitzes in your playbook.... but I can't add any to my playbook.
One reason I am trying to do this is because I play out most of my games but I Sim some of them. I have noticed that when I Sim it will use more blitzes and varied ones. When I play out the games there no blitzes suggested and I have to search through the blitzes to call one instead of looking in my custom playbook. I would love it if I could add blitzes to my custom playbook and give them weight so they will be suggested while playing the game out. Then if I need to I can also just search my playbook for the ones I want to call. Hope all of that makes sense...