put the constants in a header file

include/server.hpp

@@ -0,0 +1,12 @@
+#include <Arduino.h>
+
+/**
+ * Enter WiFi network and Proxmox information
+*/
+
+const char* WIFI_SSID = "";
+const char* WIFI_PASS = "";
+const String PROXMOX_ADDRESS = "";
+const String PROXMOX_TOKEN_USER = "";
+const String PROXMOX_TOKEN_NAME = "";
+const String PROXMOX_TOKEN_SECRET = "";

src/main.cpp

@@ -3,13 +3,8 @@
 #include <WiFi.h>
 #include <HTTPClient.h>
 #include <odroid_go.h>
+#include <server.hpp>
 
-const char* WIFI_SSID = "";
-const char* WIFI_PASS = "";
-const String PROXMOX_ADDRESS = "";
-const String PROXMOX_TOKEN_USER = "";
-const String PROXMOX_TOKEN_NAME = "";
-const String PROXMOX_TOKEN_SECRET = "";
 
 int selectedItem = 0;