"I recall somebody declaring that matter is neither created nor
destroyed, it merely changes from one form to another. You think
that might apply to the Big Picture as well?"

I think that matter IS created and destroyed AND can indeed change from one form to another. Just look at what novas and supernovae are capable of doing. It just might apply to the Big Picture as well. As to where it all started, we just don't know yet.

"It would not surprise me in the least if this Universe was created
by a being, but not the kind of supernatural God that the masses
think did the job. Nor is our Universe the only one out there."

Just as there are bubbles between stars, I think we have bubble universes. Who knows, we may be part of someone's furniture [sarcasm].

Science is a process, MORE than a process in that proof is not only called for, but has to be verified.

"It is also amazing and amusing at how a tiny species that has
existed for a mere fraction of the life of the Cosmos is so sure
of itself so soon."

Don't be (amazed nor amused).