Nawiasem mówiąc in English:

Incidentally, this room doesn't have anything like an air-conditioner. All it has is a fan.

By profession he is a lawyer and incidentally a musician.

incidentally, did you see...? / ... who, incidentally, owes me £10...

Incidentally, how did you get here? (Nawiasem mówiąc, jak się tutaj dostałeś?) That isn't as easy as it sounds, incidentally. (To nie jest takie proste na jakie wygląda, nawiasem mówiąc.)

I wouldn't blame you, incidentally.

Incidentally a motorway ramp is being constructed in the neighbourhood, a few hundred metres away, of my clinic.

Incidentally, that the gills of fish are bright red is because there are many 'capillary vessels' collected there, the same as for lungs.

by the way, I also think is really cool.

I'm from Brazil by the way.

I think we've discussed everything we need to - by the way, what time is it?