Yes, that helps. And I can see how the issue of where in the timeline you do things can be critical, at least for the Mirror function. It appears that Mirror is done differently than a Copy/Paste, in that it's NOT referencing some common underlying set of operations. With Copy/Paste it seems that no matter which instance of the object (the original or a later made Copy/Paste) you edit, the change is reflected in the other one(s). And you're saying that Mirror doesn't work like that, that you have to possibly move things around in the timeline in order to get changes reflected in the other one, AND that it only goes one way, from original to mirror.
Also, I've been having trouble moving things around in the timeline lately. There have been several times when I've tried to move a feature in the timeline and Fusion goes off doing something, showing a Busy indicator, and it just never returns.
I can see that it's handy that with copy/paste and moving features around the timeline you can effectively keep the (apparent) association between the two mirrored instances and also selectively make un-associated changes.
In my fantasy you'd be able to do a mirror (or copy/paste or copyPasteNew) and be able to say whether or not the two are related and ALSO, perhaps later, to identify which NEW edits and changes and additions to an individual instance should be independent of the other instance. I can easily imagine have a whole slew of almost-identical copies of something which have some characteristics always identical and others unique to each instance.
And, yes, I make extensive use of User-Defined parameters in order to (sometimes) be able accomplish that sort of thing.
