That's not the right place to ask , also I don't understand what you are asking about.
The tool already merge the FX layers (in the Extra features list), also I don't see any 'create' button on avatar like you say , the only thing you really have to do , is select your avatar and pet and press the 'setup' button in the tool.
I just did it like 10 minutes ago with two avatar from gumroad and it works without extra steps.
(Version SimplePetNPC_v020)
You should probably explain what's wrong with the tool and what is not working in your case.