Above is what you see when you go into SYNTH PATCH (SYNTH1 and SYNTH2) mode. Focus is given on signal routing with "virtual" patch cords that you plug into the female jacks.
What patching does is to give you control over how the audio signal (from the oscillators VCO1 and VCO2) is modulated. The arrows indicate the signal flow.
You have the destination signals all arranged in a row right below the knobs. The knob for each destination signal controls the amount of modulation. It is bi-directional, meaning that the center position turns the effect off, turning the knob to the right increases the effect of the modulation signal and turning the knob to the left increases the effect of the inverted modulation signal. Well, that's until you use VCO2 to modulate in which case the knob you plug the signal into becomes uni-directional, meaning that it has to be turned all the way to the left to turn the effect off. Turning it to the right increases the effect of the modulation signal. Yeah, it's a bit confusing.
Plugging a control signal into the PITCH IN jack modulates the pitch for both Voltage Control Oscillators (VCOs). To control just one VCO, plug the cord into VCO1 PITCH or VCO2 PITCH.
Plugging a control signal into CUTOFF IN modulates the frequency cutoff of the Voltage Controlled Filter (VCF).
Plugging a control signal into VCA IN modulates the control voltage of the Voltage Controlled Amplifier (VCA), in other words, the output volume.
The modulation signals are all aligned at the bottom, gathered in the Modulation Generator (MG) sub-panel: Low-Frequency Oscillator (LFO) with its 4 types of waves, Envelope Generator (EG) and VCO2. As you can see, the 2nd Voltage Controlled Oscillator has dual functionality: it can be used to produce sound and to provide a modulation control signal. Note that the real KORG MS-10 does not have a 2nd oscillator, there's just one.
Quite simply, you may use a patch cord from any jack at the bottom (modulation signals) to any jack just above (destination signals).