Proof of concept works. Nano can proxy requests to ESP32 via soft serial and then receives confirmation after event. Nano has a cleaner serial interface and will not throw junk into mcopy app serial listener.

.gitignore

@@ -6,3 +6,5 @@ node_modules
 dist
 
 *.svd
+*debug_custom.json
+*debug.cfg

notes/esp32_serial/esp32_serial.ino

@@ -20,6 +20,7 @@ void loop () {
     }
 
     if (cmd == 'x') {
-        Serial2.print('x');
+        Serial2.print(cmd);
     }
+    cmd = 'z';
 }

notes/nano_softserial/nano_softserial.ino

@@ -5,26 +5,36 @@
 
 SoftwareSerial softPort(SOFTWARE_RX, SOFTWARE_TX);
 
+volatile char proxy = 'z';
 volatile char cmd = 'z';
-volatile long now;
+
-volatile long start;
 
 void setup () {
+    Serial.begin(57600);
     softPort.begin(9600);
-    start = millis();
     pinMode(LED_BUILTIN, OUTPUT);
 }
-
+//////
+// Sending an x character to the nano over
+// Serial will proxy it to the ESP32 over SoftSerial
+// which will reflect it back to the Nano
+// and will turn on the built-in LED. Proof of
+// concept round trip
+//////
 void loop () {
-    now = millis();
+    if (Serial.available() > 0) {
+        proxy = Serial.read();
+        softPort.print(proxy);
+    }
     if (softPort.available() > 0) {
         cmd = softPort.read();
     }
+    if (cmd != 'z') {
+        Serial.println(cmd);
+    }
     if (cmd == 'x') {
         digitalWrite(LED_BUILTIN, HIGH);
     }
-    if (now >= start + 5000) {
+    cmd = 'z';
-        softPort.print('x');
-    }
 }