The best moves for the squat would be leg curls and leg presses. Anything outside these two is really not necessary. In fact you can get along nicely by just squatting. The bench has more and is probably the most overworked powerlift. The deadlift also has several supplemental moves like rowing, shrugs and pulldowns.
Work curls once per week when time allows.
Calves and abs could conclude each of the workouts and really should not be overlooked. Abs could be worked at home on off days if there is time. Assistance exercises could be alternated weekly or monthly if you have only time enough for one. Rowing could be done one week, shrugs the next. This also allows the lifter to strengthen numerous muscle groups and keep his lifts moving.