A week ago, reconstructing the staircase seemed overwhelming. This is why I ignored it for four years.
But, after playing with it for several days, its mysteries have been revealed and I understand how it was put together, and how much of X Y Z pieces I need to have made. The whole thing now makes sense.
I am just bursting with excitement.
And a new half-flourish can be created by making a mold of the extant one and casting a new one.
Had I invited a skilled craftsperson to just deal with the whole stair, I would have been billed, likely, $30,000 to reconstruct the stair. But I expect to spend maybe $2,000 in having components milled.