Starting with Stock BTT-Config and Old Configs as Backup

buildroot/bin/opt_set

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+
+# exit on first failure
+set -e
+
+SED=$(which gsed sed | head -n1)
+
+while [[ $# > 1 ]]; do
+  DID=0
+  for FN in Configuration Configuration_adv; do
+    "${SED}" -i "/^\(\s*\)\/*\s*\(#define\s\+${1}\b\) *\(.*\)$/{s//\1\2 ${2} \/\/ \3/;h};\${x;/./{x;q0};x;q9}" Marlin/$FN.h && DID=1
+  done
+  ((DID)) ||
+    eval "echo '#define ${1} ${2}' >>Marlin/Configuration.h" ||
+      (echo "ERROR: opt_set Can't set or add ${1}" >&2 && exit 9)
+  shift 2
+done