--- a/eric6/Utilities/__init__.py	Sat May 09 11:49:12 2020 +0200
+++ b/eric6/Utilities/__init__.py	Sat May 09 12:46:04 2020 +0200
@@ -1745,6 +1745,14 @@
             qtDir, generateQtToolName(toolname.capitalize())) + ".app",
         os.path.join(qtDir, generateQtToolName(toolname)) + ".app",
     ]
+    if toolname == "designer":
+        # support the standalone Qt Designer installer from 
+        # https://build-system.fman.io/qt-designer-download
+        designer = "Qt Designer.app"
+        bundles.extend([
+            os.path.join(qtDir, 'bin', designer),
+            os.path.join(qtDir, designer),
+        ])
     for bundle in bundles:
         if os.path.exists(bundle):
             return bundle