Using FileMaker Pro Advanced 16.0.3 on both iMac 2017 and MacBook Pro 2016, both running High Sierra with latest updates: the export records dialog is broken. See attached screenshot. The dialog shows a huge blank area where the file browser should display files and folders. And it can't be fixed: the divider between the blank space and the small bit of file browser that is visible cannot be dragged down.
Just reporting now for first time but this appeared in FileMaker 16 a while ago.