In Flow Designer, after retrieving a list collector variable from the Get Catalog Variables action, you cannot use it as the array in a For Loop action.
Release or Environment
The Get Catalog Variables action returns a list collector as a comma separated string rather than an array. Because of this, we cannot iterate through the values from the string list.
Create a custom action that uses a string as the input, parse the string into an array, then outputs the array to be used in the For Loop.