I just tried "analysis and finish against computer". It seems erratic. The backwards arrow lets me take back the last two moves (the computer's move and my prior move to that move) a couple times and then later in the practice stops letting me do another takeback-- I think there may be a limit of three takebacks. Is there a setting to allow more takebacks? Before this week I was able to take as many moves back as I wanted.
New Training Feature: Practice

thank you chess,com for restoring move take back in "finish against computer:, Next request-- could there be a way to force the computer to make a different move (that is, I selectively make a move for the computer) to try out a different line?
An easy way of achieving this is to select Analysis. In analysis mode you play the moves for both colours. When you reach the desired position you want to play on from then just select 'Practice vs Computer'.
thank you chess,com for restoring move take back in "finish against computer:, Next request-- could there be a way to force the computer to make a different move (that is, I selectively make a move for the computer) to try out a different line?
You can sort of do this now...
When you see the computer move you want to change...
1. Back up one move.
2. Switch sides
3. Make the move you want to see. Now the computer will move as YOUR color, so...
4. Repeat steps 1-2.
There might be some other things we can do to make this better... For instance, if you've backed up, it could allow you to move as either side without using the Switch Sides button. There was also some consideration given to allowing the player to "pause" the engine - and so move for both sides. Those might be worth exploring further.