It depend on the temp and humidity and also the type of lacquer used. With Deft lacquer sanding sealer, usually a couple hours is enough but it's not as hard as gloss nitro cellulose based lacquer. The gloss I'll let sit least 12 hours or maybe less on a hot dry day.

If you don't wait long enough, it may be a little gummy or shrink after you've leveled it and you'll need to apply more lacquer and sand it again.