Can you convert a non-automatic WL Breaker into an automatic WL Breaker or vice-versa?

No.  It is not possible to convert a WL breaker (with trip unit) to a WL non-automatic switch (without trip unit). Likewise it is not possible to convert a WL non-automatic switch into a WL breaker.

Aside from the technical issues involved, modifications like this convert a device of one UL product category into another UL product category and that is prohibited by UL.