Hi Hassan,
Thanks for contacting Syncfusion support.
We have validated your query for splash window in blazor application. According to that, splash window in windows forms is displayed until the window gets loaded. In Blazor, the application is loading in the browser where we can use Spinner for showing loading indication. If you are looking to design that loading indicator like windows form, we can use dialog control for that and customizing it as we want. Also, we can use Toast component also for customizing the loading window.
Could you please check and pick based on your requirement? If you need a sample for this, kindly confirm us. We will create a sample and share with you.
Regards,
Joshna L