Hi, I'm new to Arduino. As one of my firsts projects I wanted to build this simple UltraSonic Levitator called NanoLev and I was wondering if I could desolder the transducers on a HC-SR04 Range Finder and use both of them as transmitter.
That is covered in the documentation of the project you linked to.
"If using HC-SR04 sensor transducers, be sure to use the emission transducers with a T marked on the back."
Only one will have a T, because it's the transmitter...
Yes, you can unsolder the transducers on the SR04 thingy and use them both as other thingies.