For muggins I was thinking more along the lines of a scoring table:
15 +/- 0 (increases count by 2)
Pairs +/- 0 (increases count by 2)
Straights 0 +/- 3 +/- (number of straights, length of straight)
Flush 0 +/- (counts 0, 4, 5 points for a flush)
Nobs 0 +/- (0 or 1 for the Jack)
Player enters their score and opponent has a chance to disagree with it, changing the part they believe is wrong or accepting the score.
Only slightly different would be when playing from a hand but the same idea would be there. A player plays a card from their hand and can select points they should get for the play, some of the scoring would go away from scoring a hand but 30/31 would need to be added as an option.
It would add some time to the game but would be easier than clicking a counter to increase or decrease by 1, and showing what was scored would be more obvious to the players. I realize you have several changes ahead of it in the priority, but I think there are ways to make it pretty straight forward. (For that matter it might be nice to see a score breakdown in the current mode, it would help new players understand what was being scored.)
15 +/- 0 (increases count by 2)
Pairs +/- 0 (increases count by 2)
Straights 0 +/- 3 +/- (number of straights, length of straight)
Flush 0 +/- (counts 0, 4, 5 points for a flush)
Nobs 0 +/- (0 or 1 for the Jack)
Player enters their score and opponent has a chance to disagree with it, changing the part they believe is wrong or accepting the score.
Only slightly different would be when playing from a hand but the same idea would be there. A player plays a card from their hand and can select points they should get for the play, some of the scoring would go away from scoring a hand but 30/31 would need to be added as an option.
It would add some time to the game but would be easier than clicking a counter to increase or decrease by 1, and showing what was scored would be more obvious to the players. I realize you have several changes ahead of it in the priority, but I think there are ways to make it pretty straight forward. (For that matter it might be nice to see a score breakdown in the current mode, it would help new players understand what was being scored.)