Birth IDs cannot be assigned, no. Because they must always be 100% unique for each particle - no exceptions. If I allowed users to assign birth IDs, I'd open up the possibilities that users could break that rule, which could have disastrous implications all throughout tyFlow simulation logic.
Internally you can assign up to 65536 different export or simulation group values. You're just limited to 16 groups in the UI because that's the maximum number of bitflags an unsigned short value can have. But you could use a Script operator or Custom Properties operator to assign more than 16 values to a simulation/export groups channel. This ability can allow you to treat groups more like clusters.
Internally you can assign up to 65536 different export or simulation group values. You're just limited to 16 groups in the UI because that's the maximum number of bitflags an unsigned short value can have. But you could use a Script operator or Custom Properties operator to assign more than 16 values to a simulation/export groups channel. This ability can allow you to treat groups more like clusters.