In Mockups 2, I always wished it was possible to add a text label to an icon after putting it in a mockup. This wasn’t possible then, and isn’t in v3 either. Furthermore, if you search for the icon in the quick-add search box (a great feature by the way), you have no way to select the “icon with label” option.
It’s frustrating to have to delete an icon, re-add it with a text label and then replicate your choices of icon type, size, colour, placement etc. Seems it would be quite simple to incorporate the option for a label in the properties inspector and then not have to maintain the two distinct object types.