The scene preview is not updated in real time when you work on a model : it changes only when you release the mouse button . I remember that one year ago, i've asked Metacretins about the fact that once the preview window is closed, you can't make it reappear . They answered me that it was a bug and there was nothing to do about it except saving the file and reopen it . Hopefully, this will be fixed with the new patch, wich is planned for ... well ... a long time ago ! ;) litst