Taiizor
It's working as it should now.
The css line in the wwwroot/index.html is important. Because it enables custom css codes of razor files.   
Hot Reload works fine for MainLayout.razor.css. https://user-images.githubusercontent.com/41683699/200972166-afc7de68-f01d-499e-9730-0221a2494970.mp4
> @Taiizor what version of VS are you running? I believe it's fine in 17.4. 17.5 appears to have the regression. 17.4.0. But Hot Reload for app.css doesn't work.
> > But Hot Reload for app.css doesn't work. > > Are you essentially seeing this? > > Screen.Recording.2022-11-09.at.4.29.42.PM.mov https://user-images.githubusercontent.com/41683699/200973989-2aa1685c-0b16-4b26-94bc-c9be8123e417.mp4
There are many button components. If you wish, you can do PR work on any buttons you want. Because i see you know something about it.
 If you tell me which component it is, I might be able to help.
it works fine in my tests   
You can customize Metro components the way you want using StyleManager. Customizable sample theme file is below. https://github.com/Taiizor/ReaLTaiizor/blob/develop/src/ReaLTaiizor/Resources/Metro/Metro%20Theme.xml How to use this theme file is shown in the example below....
which button?