There's lots of different recipes for it.
There's dozens of recipes for Swedish bitters. Bob asked about one of them in this comment. His blend contained these herbs:
"Manna (stem) Fraxinus ornus, Angelica (root), Zedoary (root), Aloe (leaves), Rhubarb (root), Senna (leaves), Myrrh (stem), Carline Thistle (root) Carlina acaulis, Camphor, Black Snakeroot (root) (Rhizoma Cimicifugae), Valerian (root), Cinnamon (bark), Cardamom (fruit), Saffron (pistil), water & alcohol."
Digestive: angelica, zedoary, cinnamon, cardamom, saffron, myrrh (in small doses)
Laxative: aloe (if green parts are used), rhubarb, senna
Demulcent: manna, aloe (if clear juice is used)
Cathartic: carline thistle (in large doses)
Diuretic: carline thistle (in smaller doses)
Clears the sinuses: camphor
Very weird in this blend: black cohosh (Cimicifuga)
"What would you guess this concoction might actually be useful for?"
Somewhere on the web Swedish bitters were described as the current theriac. Theriac is a herb (&c.) blend from about 2000 years ago that was meant to cure everything, including poisons.
This particular blend is mainly (but not completely) digestive, something to be taken after you've eaten.
The senna in the blend can be addictive: you won't be able to take a dump without it, if you've been taking it daily for long enough. Long enough being 2 weeks, give or take a few days.
"I learned only a very little about bitters in chiropractic college. They seem to posess a lot of potential."
Bitters are fairly simple: the bitter taste in your mouth starts up salivation, which starts up the juices all along the digestive canal, in sequence.
Do bitters 20-30 minutes before every meal if you have a sluggish digestion (you balk at, say, raw cabbage, or fat foods, or similar), and do bitters 20-30 minutes before every meal if you don't have a gall bladder, or if you have trouble with fat digestion.