The request is in the title; but I do not know if I could read the version in time: the loading of B4A is 50 times faster than Android Studio and 100 of Visual Studio
The splash screen is a feature of WPF framework. I believe that the only way to add the version is by creating a new image every time. Not sure that it is worth the efforts...
You can always go to about and see the version. Other applications, even the browsers have their version in the about section. Having it as a splash or a toast will not make any difference, it will only slow it down. As you said, B4A loads faster than other IDEs 50-100 times.