If Object A is empty then create new, otherwise use this one. How to assign?
The thing is, when I create a new object, I can't just assign it to Object A, which I would want to do because I will use it for several activities and don't want to go DRY. I guess I have to use subflows for this, but I was wondering if there is another solution?
You should just use a subflow for this which returns the object. In the subflow either fetch or create the object and let the microflow return the object. In your main flow you then always have that object that you can change later in the mainflow without having to concern about if it is a retrieved object or just newly created.