Just a Message if we try to drop decision or switch in sequence tool.

Hi There

Sequence tool is very useful while developing a large workflow and now my workflow looks very simple. 
I would really like to appreciate the idea of developing a sequence tool.
But when I try to drag and drop a workflow with decision or switch, it wasn't allow me to drop.
then I tried many times and concluded, this is not working properly, but anyhow I realized later that sequence doesn't allow decision and switch. 
So if we have a validation message when user try dragging a decision or switch tool inside the sequence it could be very nice.

Thanks