Leozelig,
I thought I had both damage values showing up when I created the Item XML back on my unofficial DCC ruleset. I think I listed the damage like [Dagger 1d4 slashing (1d10 slashing)] or some such.
Both damage lines showed up in the Action tab and the user just had to select the correct one to drag to the Creature/Chat when resolving the attack.
I will look again.
Kirklandone