i have some 20x, can i put it under my tongue instead of smoking it??

yes. It won't be like smoking it though. And you'll have to keep it under your tongue for about 20 mins, and don't swallow.

You can use it sublingually, but it will not be much more effective than plain leaf. I’ve read that extracts are not very good for quidding/sublingual use. (Never tried it myself – so if you try it and have success, please report back!)

doesnt work too well IMO...not as well as quidding whole leaf since quidding covers more surface area..I mean it does work somewhat but seems a waste..I would just get some whole plain leaf and rehydrate it..or make a sublingual tincture with the extract if you must.

Yes, what fractal said. It doesn't work any better than plain leaf really. Make a tincture with it if you don't want to smoke it.