Hi experienced users, I have just started learning design with easyEda for few days.
I have a question: If we could save a schematic module as a "blackbox" with only input and output ?
For example:
I have a circuit called Full-adder, how could I save it "as a module" with a symbol with 3 input, 2 output, and make sure that I could use the "symbol" in simulation?
(I would like to make a circuit like this, with (1, 2, 3) = (A, B, Cin) and (4, 5) = (Sum, Cout):
)
Many thanks for your helps
Brand new interactions and interfaces. 
Easy to use and quick to get started. 
What you are asking about is whether hierarchical design is possible in EasyEDA (like in a native installation of LTspice).
Sadly, this is not supported in EasyEDA at the moment.
However, you could use the 74HC283 4-bit binary full adder with fast carry that is in the library:
There used to be a half and a full adder primitive in the EElib library but it has not been updated from ngspice to LTspice. If I get the time, I will see if I can add them to the library.
BTW: don't forget to remove the short at the inputs to U5...
:)