Hey @iain !
So, EditorX is a cascading editor, meaning the changes you make cascade down to lower breakpoints. What you change on the larges breakpoint will trickle down to the breakpoints below. But changes to smaller breakpoints won’t effect larger breakpoints.
There are a couple of exceptions to this rule, like data changes, or structural changes (reparenting elements etc).
Here’s a couple of links that will hopefully point you in the right direction: