Is there a way to scale outline size when changing the size of the curve? In previous versions, there was a scale outline checkbox, but I don't seem to be able to find a way to do this now. I really want to keep it a curve, and not convert the line to an object if possible. Thanks!
I'm using the Windows version, so I don't know exactly how it looks on a Mac, but...
In the Properties docker, on the Outline tab, there is a checkbox for "Scale with object".
In the Windows version, there is a section of the user interface there that is by default collapsed, and "Scale with object" is found in that section. You may need to expand that section of the UI in order to see it.
In CorelDRAW for Mac the "Scale with object" Outline setting is found at the bottom of the Properties inspector (same as in the Windows application):