There are functions called KRC_writesysvar() within the MxA library, you have to define the index number for this function and then write your own case switching code inside mxa_sysvar.src on you robot controller to call out specific modules.
Of course, you also need to reset the trigger signal for KRC_writesysvar() on your PLC(or anything else) to make it run after activation.
Could you give more details about it? We are also recently need to use this feature. Thank you.