Set an MIGX variable field to a certain value

Hi there,
I added a field "available" in a complex MIGX varibale to store a boolean value: yes==1||no==0

Now I need to set "available" to "1" for every resource with certain template.
Is there a "MIGX" way to do that?

Or would I have to code it? Like "get TV (with that JSON string inside), modify the JSON, store the TV"?

Since the new field "available" isn't yet represented in the JSON, how to inject it properly?

thanks
Oliver

you will need a custom script.
Here's an example:
https://github.com/Bruno17/MIGX/blob/master/core/components/migx/processors/mgr/setup/setup.class.php#L47