Hi,
I’m trying to use the split screen to keep two docs open at once. Firstly, I can only see the option split vertically. Secondly, regardless of which window I activate(darker blue line under doc heading) only the bottom window changes when I select a new doc. Is there a way I can change this so that the top window is the one that changes when I click a different document?
In Windows Scriv, holding down the Alt key toggles the button between vertical/horizontal splitting. Not sure which button this would be on the Mac, but with experimentation you’ll figure it out. You can also control via the menu. View > Editor Layout.
Confirm how you have Binder Selection Affects set in the menu. Navigate > Binder Selection Affects. To have Active doc change would equate to setting Binder Selection Affects = Current Editor. To have top window change would equate to Binder Selection Affects = Top Editor.
Or you could swap editors. View Editor Layout > Swap Editors.
I change these particular settings constantly, depending on what I’m doing, so you might find it helpful to memorize them. 
Best,
Jim
Jim, you are an absolute star. This sorts out my problem. Thank you very much!