Double Bass Symbol for repeat three times?

[DoubleMIDI]

On the other hand music typesetting existed since the late renaissance.

They didn‘t had ledger lines for music typesetting at that time to keep the already high number of different typesetting parts low, so they changed keys to avoid ledger lines.
There were several f-clefs, all kind of c-clefs and also several g-clefs.
Every key, note length at any position at the staff and length were a separate part that was lined up for printing.
So they only set up a single page printed it, then reused the parts from this page for the next one.
For a later reprint you need to do the whole work again.

So engraving would do a reprint much easier as long as you have enough material and space to keep it. It also looks a lot nicer.

 

[dreamadream99]

Is there a standardized symbol or way to write repeating the A part 3 times?

Yes.

if all three A sections are the exact same, then a standard left repeat sign and right repeat sign, with 3X’s written above it.

If the A sections all start the same, but one or more ends differently, then separate numbered endings for each different ending.