Here's a test project containing Pic3D and US4DCyl both with segmentations:

When you wanted to segment on an "non-reinited" segmentation, there used to be a simple, immediate warning that you should reinit the segmentation first. It was already hard to understand for users as they probably do not know what "reinit" is and where to find it.

Now the warning is even more cryptic: "Please perform a reinit on the segmentation image inside the entered Render Window!". What is reinit? What is a Render Window? What does entered mean? None of this will make sense for the common user.

On top of that the warning now is only shown when a tool is active and the cursor is on a render window. And there's more cryptic text as overlay: "Interaction is not possible because the render window is not aligned." Again, what is a render window? What does align mean? Aligned to what?

I understand that all these changes were done with the mxn multi widget in mind, but in my opinion it made the situation worse for our common use case of having the std multi widget. Even without all the tech speak the warnings are not only unnecessarily delayed now for this case, but also wrong, since there is no render window specific reinit as far as I know. In addition, I can still interact with the "blocked" render window and continue using tools.

We definitely need to fix and improve the current situation before the upcoming release.