I know that traits can be made with Zerbu's BATF, and traits made with that program use the previously used animations. (First, it is the 'thinker'/'ambitious' animation, and the next trait you have last used)
Have non-default poses made that much progress for custom traits?
I don't have much experience with custom traits but it looks like they have an ASM parameter in their SimData called cas_trait_asm_param that tells the game which animation to select in its ASM. I think to add your own would probably require overriding the CAS ASM to add animation references that correspond to a new parameter, which would make it conflict with any other trait that has a custom animation.
Please do not PM me with modding questions. Post in the Creator Help forum.
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