Without knowing if you're on oxygen at night, I am but still wake up and have to clear mucus.
I sleep with my head elevated at about 30 degrees. I drink Mullein tea twice a day once in the morning and once in the evening. [Some people take Mucinex] It has cut my mucus down to less than 1/2 of what it used to be. Still I wake up once a night and first thing in the morning and have to clear my mucus. Drinking plenty of water helps keep it thin.

You see your lungs rest and clear out all the dust and germs you have inhaled all day at night while you sleep. It always has but it normally just gets swallowed. We produce more mucus because of the damage to our lungs. Thus it is thicker and more than normal. So we need to wake up and clear it.

I use Carbocisteine which i find great for mucus thinning BUT with exacerbations I get my wife to use a percussion massager on my back (in the area of the lungs) which releases lots of mucus quite easily.
Hope it helps. (Try Amazon "percussion massager - around £20)

You may need oxygen at night. That's how i started on oxygen.