As shown in the entertainment village arc and train mugen tanjiro used a recovery breathing to slowly recover from the attacks and even heal serious injuries
Now my idea is the ability to switch from normal breathing to recovery by pressing a key they have 2 separate bars but the recovery one drain as fast as breathing trained with only the 2nd gourd but only if you unlocked it
Using recovery drains instantly the breathing bar, but using breathing doesn’t affect the recovery bar
Recovery can be unlocked only after lvl 75
Can be only upgraded by max 2 gourds
Edit: you don’t necessarily need a breathing form to learn recovery breathing