In their data sheet, they say that "Nuclear counterstaining can be performed after TrueVIEW treatment. [...] For DAPI staining, we recommend using DAPI at 5 μg/mL in PBS buffer for 10 minutes, and then mounting with the included VECTASHIELD Vibrance Antifade Mounting Medium."
They also show staining images with DAPI, so it should be fine.
Vector Labs also offers the TrueVIEW Autofluorescence Quenching Kit with DAPI, SP-8500, which includes DAPI in the mounting medium. This allows quenching and DAPI staining with shorter steps.
Byron Hsu In the TrueVIEW Autofluorescence Quenching Kit brochure, does incubation mean putting the solution inside an incubator for 5 min or just letting it stay outside?