The circuit diagram above uses a Feather M0 Express and OLED breakout. Much of the wiring is taken care of by using a Feather and wings as we do here. All we need to build is a wing with the rotary encoder, level shifter, and servo header.
There's a level shifter to drive the servo with a 5v signal. This avoids any potential issue with a 3.3v signal not being a high enough voltage signal.
Using Feathers, wings, and a Feather doubler/tripler wing is a nice way to prototype a design even if you want make it more compact and put it in a case for a final build.
The rotary encoder fits nicely at the "usb" end of the proto wing, straddling the 3.3 and ground bus lines. The servo header goes at the other end, with the level shifter fitting neatly between them. If you use right angle header as shown here, there's just enough room to fit everything without the header pins extending beyond the edge of the wing.
Here, you can see the wiring. Colored wire is used:
Once the encoder/servo wing is built, snap it all onto the triple, connect a servo and power via USB.