けど、一晩加湿器つけっぱなしで朝になると窓が結露してドボドボ・・・。

、・・・。

But if you leave the humidifier running all night, by morning the windows are covered in condensation and dripping wet...

Literal

But, all-night humidifier left-running-[ぱなし-で] morning becomes [conditional-と] window [subj-が] condensation-doing soaking-wet...

つけっぱなし (from つける + っぱなし) means 'left on / running unattended' — the ~っぱなし suffix marks something left in a state with neglect. 結露 'condensation' is a technical compound (結 'form' + 露 'dew'). ドボドボ is a mimetic for liquid dripping heavily or overflowing. The trailing ・・・ leaves the unpleasant consequences to the imagination.