Problem with Mail Rules dialog box in High Sierra
I'm in the midst of setting up a new iMac running OS 10.13.2.
In Mail, I've encountered an issue with the dialog box where I create the rules to filter my incoming/outgoing messages. As I add more filters to a particular rule, the 'Perform the following actions' box shrinks a little bit with each entry. If the list is long enough, the buttons within that box almost disappear from view -- to the point that they cannot be selected.
At first I thought that there was a problem with the rules I was creating, so I deleted them all and started over, only to have the issue re-occur.
Has anyone else encountered this, and if so, discovered a fix?
iMac with Retina 5K display, macOS High Sierra (10.13.2)