How to trigger NodeMCU sketch from Arduino Leonardo Micro Pro?
HW part:
It's like button, simply connect arduino micro pin to nodeMCU pin and GND of arduino to GND of nodeMCU.
It's also good idea to use two resistors as voltage divider because arduino micro works with 5V and ESP8266 (nodeMCU) with 3V3. 5V can destroy ESP8266 but this thing is still not really clear.
Resistor divider connect as in this link link about resistor divider for uart but instead of TX put arduino micro and instead of RX nodeMCU.
resistor divider schematic

Code part:
On the arduino micro part use:

In void setup():
pinMode(PIN, OUTPUT);

In your marked place:


digitalWrite(PIN, HIGH);
delay(100);   //short wait time
digitalWrite(PIN, LOW);

nodeMCU part:

In void setup():
pinMode(PIN, INPUT);

Remove everything from void loop() and put there this:


if(digitalRead(PIN) == 1) pushover(&quot;OMG, Yes it works!!!&quot;);

In both codes select the PIN according to your choice.