Is there a way to connect a button to a Raspberry Pi 3B+ without a breadboard? If so, how? Could you give a diagram and explain? I am only a beginner so please make it easy to understand. Also I would like to avoid soldering. Thanks in advance.
You could do it with the female to male jumper wires and some alligator clips, but why would you want to go that much trouble to avoid soldering or a breadboard?
For a diagram, wire it exactly like the diagram in this picture, but skip the breadboard and wire directly from GP2 to one side of your switch and from the other side of your switch to a GND pin.