I don’t know why, but the most frequent request is for 6 days.
I tried to include all the most interesting things as much as possible. In some places, there are sections with a lot of serpentines. If your skills are not confidently average or you just want less driving, write, and I will trim the route.

1st day (Sv. Stefan, Bar, Ulcin, Skadar NP, Rijeka Crnojevica, Podgorica)
2nd day (SH20 panoramic road, Prokletje NP,   Moraca Canyon, Kolasin)
3rd day  (Đurđevića Tara Bridge, Tara canyon, Durmitor, Nedajno, Mratinje dam, Piva lake)
Unfortunately, the road P4 (Tara River Canyon) is still under reconstruction. Have to use another road. Also, check recommendations about the Durmitor part here 
4th day (Komarnica Canyaon, Durmitor, Trsa, Sedlo pass, Prtas,  Savnik, Kapetanovo lake, Niksic)
Unfortunately, google.maps will lead you in the dead end near Kapetanovo Lake. Don’t worry, go back a bit and go around the wall you’ll hit on the right. The road is obvious, and there are signs.
5th day (Monastir Ostrog, Bileca Lake, Kravica Waterfall, Mostar)
6th day (Stolac, Monastir Tvrdos, Herzeg Novi, Risan, Perast, Kotor, Kotor serpentine, Cetinje)