Miniblinds don’t last forever:
The plastic frame failed at the pull cord opening, obviously a weak and, alas, non-repairable point.
A quick trip to Lowe’s produced a new miniblind with mounting hardware completely different from the old one. This came as no surprise, as every new miniblind differs from all previous ones; miniblind mounting hardware is not strongly conserved.
The broken frame fit into the plastic end caps mounted just beyond the scarred paint marking the bracket location required for the previous miniblind:
Note that the caps mount with a single screw in the homebrew bracket’s face, which has two holes to match the previous-previous cap.
Although the shiny new hardware had two slots, they neither lined up with the existing bracket holes nor extended quite far enough vertically. I lined things up, marked and drilled a single midline hole in both the new hardware and the old bracket, and reused the old screw and nut:
Moving the bracket back to its previous-previous location exposed the scarred paint under the previous position:
Fortunately, it’s hidden by the installed miniblind.
That was, all things considered, easy …