Fixes #83513 - adds custom titlebar note

src/vs/workbench/common/theme.ts

@@ -593,13 +593,13 @@ export const WINDOW_ACTIVE_BORDER = registerColor('window.activeBorder', {
 	dark: null,
 	light: null,
 	hc: contrastBorder
-}, nls.localize('windowActiveBorder', "The color used for the border of the window when it is active. Only supported in the desktop client."));
+}, nls.localize('windowActiveBorder', "The color used for the border of the window when it is active. Only supported in the desktop client when using the custom title bar."));
 
 export const WINDOW_INACTIVE_BORDER = registerColor('window.inactiveBorder', {
 	dark: null,
 	light: null,
 	hc: contrastBorder
-}, nls.localize('windowInactiveBorder', "The color used for the border of the window when it is inactive. Only supported in the desktop client."));
+}, nls.localize('windowInactiveBorder', "The color used for the border of the window when it is inactive. Only supported in the desktop client when using the custom title bar."));
 
 /**
  * Base class for all themable workbench components.