Unfortunately, optional parameters need to be optional in both .<filename>_vars() and .<filename>_main()

customize.dist/src/less2/include/avatar.less

@@ -5,7 +5,7 @@
     @avatar-width: @width;
     @avatar-font-size: @width / 1.2;
 }
-.avatar_main(@width) {
+.avatar_main(@width: 30px) {
     --LessLoader_require: LessLoader_currentFile();
     .avatar_vars(@width);
     --avatar-width: @avatar-width;

customize.dist/src/less2/include/checkmark.less

@@ -11,7 +11,7 @@
     @checkmark-radio-size: @checkmark-dim1 * 3;
 }
 
-.checkmark_main(@size) {
+.checkmark_main(@size: 20px) {
     --LessLoader_require: LessLoader_currentFile();
     .checkmark_vars(@size);
     --checkmark-size: @checkmark-size;

customize.dist/src/less2/include/creation.less

@@ -12,8 +12,8 @@
 };
 
 .creation_main(
-    @color,
+    @color: @colortheme_default-color,
-    @bg-color
+    @bg-color: @colortheme_default-bg
 ) {
     --LessLoader_require: LessLoader_currentFile();
     .creation_vars(@color, @bg-color);

customize.dist/src/less2/include/help.less

@@ -8,7 +8,10 @@
     @help-text-color: contrast(@help-bg-color-l15, #fff, #000); //@color;
     @help-link-color: contrast(@help-bg-color-l15, lighten(spin(@bg-color, 180), 10%), darken(spin(@bg-color, 180), 10%));
 }
-.help_main (@color, @bg-color) {
+.help_main (
+    @color: @colortheme_default-color,
+    @bg-color: @colortheme_default-bg
+) {
     --LessLoader_require: LessLoader_currentFile();
     .help_vars(@color, @bg-color);
     --help-bg-color-l15: @help-bg-color-l15;

customize.dist/src/less2/include/toolbar.less

@@ -33,9 +33,9 @@
 };
 
 .toolbar_main (
-    @color, // Color of the text for the toolbar
+    @color: @colortheme_default-color, // Color of the text for the toolbar
-    @bg-color, // color of the toolbar background
+    @bg-color: @colortheme_default-bg, // color of the toolbar background
-    @warn-color, // color of the warning text in the toolbar
+    @warn-color: @colortheme_default-warn, // color of the warning text in the toolbar
     @barWidth: 600px // width of the toolbar
 ) {
     --LessLoader_require: LessLoader_currentFile();