From what I know, in 5e, the Rogue needs Advantage on a roll in order for Sneak Attack to be added.
That said, if the Rogue is invisible or hiding before the attack, it should have Advantage and cause Sneak damage.
Other example : flanking with an ally should give Advantage and cause Sneak damage.
SUGGESTIONS :
- when hovering or targeting with the Sneak attack icon, an indicator should show if it is relevant (will apply) or not ;
- should be a clearer indicator for Advantage / Disadvantage on a target before attacking (I am pretty sure there is one, I am guessing, but have not spotted it yet honestly). Will look again.
In both BG3 and 5e you don't need advantage on the attack roll to get a sneak attack if there is an enemy within 5 feet (1.8m) of your target (i.e. a party member or npc hostile towards your target and within melee range of your target). That being said, I'm all for the idea for some kind of indicator that a sneak attack is possible from current position.
