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On your Q6 the lower input is incorrectly connected. The wire pans out for too much so both the Q7 and Q8 are disconnected.
There is a simple trick to find such problems: just play with Edit/Select... menus to see where are your wires and floating elements and what not.

Hi, It depends on what exactly you need. If you want the program to synthesize a circuit from your truth table then the answer is no. The program can not do this. If you need implementation of your truth table to be used in your project you can use ROM. Simply drop a ROM module with as many address ...

Nice

Hello,
There is no any circuit that you can build yourself. You can build JK or T flip-flops yourself so there is no need to add it to software.
If you don't want to build it, you can always import it from samples of other user's project here on this forums.

You probably get more answers if you ask in English.

Precisely, your circuit can't get to any stable state while your add button is pressed down.

Hi, First of all if you have not yet read about the oscillation please read it here: https://logiccircuit.org/oscillation.html In your circuit you are using flip-flops with clock that is working by level. So when the Add button is pressed each flip-flop is storing the data its receiving on it’s inpu...

You can build such component yourself. Just create new circuit, put 1x1 let matrix, make needed connection and mark the circuit as Display. You will have any color LED.

As I mentioned it's already implemented. For practical use please see this topic:
viewtopic.php?f=3&t=9789&p=9661&hilit=traffic#p9661

You did not mention the countdown display before. The shift register is for controlling the traffic light itself. The countdown is different story. For more specific discussion please attach your project and provide better description of what you are trying to build.