Game attributes can not be created dynamically. And you can not set a Game attribute without a name. For this reason I create a predefined Game attribute before use in an extension. And if you do not know how many you're going to use, this is a problem.
As suggested, easier to use lists as game attribute. Instead of use names of lists with text, you put numbers as name and use positions in list: 0,1,2,3,4,5, etc. Then uses a event with a loop to iterate.
For example, event set_all_true
var number = 0;
set list (number) = true;
set number = number + 1;
trigger event end
With events and updates you control when to reset or change true to false and vice versa.
Changing attributes in update does not cause memory problems. However, using much events therefore depends frequency of changes.