Ah, yes. You can edit mouth and face very well in the studio. Sorry, you used the right word, I am the one who didn't realize you were talking about the scene, I thought you were replying to my post with the cards.
In the Studio, the best way to do that is using the HS2PE icon at the bottom, Advanced Mode, Blend Shapes. There you can edit the eyes, eyebrow, mouth, tongue, teeth...
I also used AiLegend's Realistic Tongue mod, because unlike the game's original tongue, the Realistic Tongue mod has individual nodes for several segments of the tongue, which makes it easier to pose it.
You basically add it as a normal item, resize it and move it into the girls mouth. It doesn't replace the real tongue, it is just a prop.