I've run across a number of abilities in games where the effect is something along the lines of "If the d20 shows 9 or less, treat it as if it rolled a 10." This is different from a re-roll because you do not re-roll the die on the excluded values, you raise them instead. I have yet to find a method that allows me to properly express this.
I can imagine two ways this could be done. One is allowing flat numbered in grouped values ("{d20, 10}k1," which currently doesn't work), which will be cumbersome for the player but still workable and potentially useful in other situations. The other is to add in a new letter, so you could have rolls like d20m10, as in "d20 minimum value is 10" (For max, you could capitalize, or have m be shorthand for "min" and have "max" be usable if fully typed, similar to dl and dh"
