### Godot version

4.0.beta12

### System information

Windows 11, RTX 3080

### Issue description

When a Window Node is created with it's Transparent flag set to true and Project Settings --> Display --> Window --> Subwindows --> Embed Subwindows is false, the Window has a black background. By cycling the transparent flag from false and back to true again, during runtime, the window's background then becomes transparent. 

### Steps to reproduce

Attempt to create a Non-embedded Subwindow with a transparent background using the appropriate flags. 

### Minimal reproduction project

Note: this project is from Reddit user [gongpha](https://www.reddit.com/user/gongpha/) and his Reddit post [Learning a Godot 4.0 Window node](https://www.reddit.com/r/godot/comments/xr8yxn/learning_a_godot_40_window_node/)

https://github.com/gongpha/godot4-window-test
RtlGetVersion(&os_ver);
		}
		FreeLibrary(nt_lib);
	}
	
	HMODULE ux_theme_lib = LoadLibraryW(L"uxtheme.dll");
	if (ux_theme_lib) {
		ShouldAppsUseDarkMode = (ShouldAppsUseDarkModePtr)GetProcAddress(ux_theme_lib, MAKEINTRESOURCEA(132));
		GetImmersiveColorFromColorSetEx = (GetImmersiveColorFromColorSetExPtr)GetProcAddress(ux_theme_lib, MAKEINTRESOURCEA(95));
		GetImmersiveColorTypeFromName = (GetImmersiveColorTypeFromNamePtr)GetProcAddress(ux_theme_lib, MAKEINTRESOURCEA(96));
		GetImmersiveUserColorSetPreference = (GetImmersiveUserColorSetPreferencePtr)GetProcAddress(ux_theme_lib, MAKEINTRESOURCEA(98));
		ux_theme_available = ShouldAppsUseDarkMode && GetImmersiveColorFromColorSetEx && GetImmersiveColorTypeFromName && GetImmersiveUserColorSetPreference;
		if (os_ver.dwBuildNumber >= 22000) {
			dark_title_available = true;
		}
	}
	
	HMODULE wintab_lib = LoadLibraryW(L"wintab32.dll");
	if (wintab_lib) {
		wintab_WTOpen = (WTOpenPtr)GetProcAddress(wintab_lib, "WTOpenW");
		wintab_WTClose = (WTClosePtr)GetProcAddress(wintab_lib, "WTClose");
		wintab_WTInfo = (WTInfoPtr)GetProcAddress(wintab_lib, "WTInfoW");
		wintab_WTPacket = (WTPacketPtr)GetProcAddress(wintab_lib, "WTPacket");
		wintab_WTEnable = (WTEnablePtr)GetProcAddress(wintab_lib, "WTEnable");
		wintab_available = wintab_WTOpen && wintab_WTClose && wintab_WTInfo && wintab_WTPacket && wintab_WTEnable;
	}
	if (wintab_available) {
		tablet_drivers.push_back("wintab");
	}