Sorry if I misunderstood, but did you not just say that 10 was an option? Any options that you aren’t presented with beyond that likely has to do with the rule that you can only build the columns for three numbers on each turn.

For instance, if the first roll in a turn is 3, 5, 4, and 1, then the options would be 5 and 8 or 4 and 9. Let’s say you pick 5 and 8. Then, let’s say your next roll is the roll you described: 4, 6, 1, and 2. In this case, your options would be, as you said, 3, 5 and 8, 6, 7, or 10. 3 and 10 isn’t an option because then you would be building the columns for 3, 5, 8, and 10 in the same turn, which is over the maximum of three per turn. Ditto for 6 and 7. 5 and 8 would be okay because you’ve previously built in those two columns and so this would keep your total at two. Any of the other combinations of two dice (3, 6, 7, or 10) are okay because selecting those would only build in one more column instead of two, keeping your total within the maximum.

Sorry for being so long-winded but I hope this helps.