Very good question. I've been thinking about the same already several years. And I probably know why you need it - you want to save a custom object and after call it as a macro and you want to use A,B and ZZYZX parameters of called macro in the main script - for example to place boundary hotspots, or find out centre of called object and place it by it's centre (for example for handle).
Looks like impossible. Unfortunately I/O Text Add-On cannot read GSM files, only txt or gdl, otherwise would be possible to set the script to scan the macro for these variables.
n = REQUEST ("ASSOCLP_PARVALUE"...) works only with labels, markers and property objects.