The analysis board gives you the option to "Finish Vs Computer". The icon for this can be found towards the lower right of the page just below the game controls. It looks like a hand holding a pawn.
Setup position against computer

Right. Thank you!
Btw, when you are setting up the position and try to remove unnecessary pieces from the board by dragging them beyond the top edge of the board, the menus are disturbingly close and open unintentionally. I don't think they should open if you are holding the mouse button down already when entering the menu area.

I can see how that is annoying. However, you can drag the pieces off the board from any edge, not just the top one. Alternatively, if you want to drag it off the top, you could adjust the top menu so it is at the side of the page.

From the starting position the easiest way to drag black pieces off the board is the top edge. Otherwise I like the menu on top.
I now managed to checkmate the computer from my setup position. A message box opened with a button "Retry" in it. I clicked it and it took me to the standard chess starting position. I would have expected it to let me play the same initial setup position again.

I now managed to checkmate the computer from my setup position. A message box opened with a button "Retry" in it. I clicked it and it took me to the standard chess starting position. I would have expected it to let me play the same initial setup position again.
That is not how it works, but maybe it should. If you think so, I encourage to further submit this via the "Make a Suggestion" interface under "Help".
If I recall correctly, you should also be able to simply go back through the moves and start over that way.
Is there a way to play a setup position against the chess.com bot (which is Stockfish I guess) in chess.com? In other words, to practice a drill that is not found in the chess.com drill set. I would like to practice K+Q vs. K + R positions, which, btw, should be included in the drill set, too, imo.
The analysis tool does not solve the problem because when I practice I do not want to see the computer's thinking lines but I do want the opponent to make its moves automatically.