extra damage dice (Vigilante w/Hidden Strike)

[Slothy]

Hi,

I am playing a Vigilante with Hidden Strike ability, but HLO doesn't give me an option to add the 1d8/1d4 extra damage as per the description. I was hoping that the system would add it similar to sneak attack damage for a pf2e rouge.

"A stalker deals an extra 1d8 points of precision damage on melee attacks (or ranged attacks from within 30 feet) against foes who are unaware of his presence, who consider him an ally, or who are made flat-footed by startling appearance (see page 17). This extra damage increases by 1d8 at 3rd level and every 2 vigilante levels thereafter.
A stalker vigilante can also deal hidden strike damage to a target that he is flanking or that is denied its Dexterity bonus to AC, but in these cases, the damage dice are reduced to d4s. A stalker can deal hidden strike damage against targets with concealment (but not total concealment)."

I was wondering if there was any way of adding this via a temporary adjustment to allow me to select an extra dice on my attack (I would probably need to create two depending on if I was flanking (1d4) or not (1d8).

Thanks

Andy