The tongue is a muscle. As with any muscle, it can be trained and strengthened.
Open mouth posture is unhealthy not just for the formation of your facial bones, but also for your health.
Drs Drew go over proper swallow with their patients and teach them where their tongue should be during a swallow and throughout the day.
Tongue on the roof of the mouth, lips sealed. Breathe through your nose. Swallow with tongue in the position as well. Try it!