It works, but I am wondering there is a "clean" way to obtain the intended result.No, that's the sort of trick you have to use. Unless you set "KeepEmpty" to 1 in your theorem environment, which would allow you not to put the ~.
Ok, I see.BTW, I discovered that using an empty red box is a better work around, since the exported latex is clean as I intended.
Thanks Fabio
