[Gui] Show Preferences page by name rather than index

src/Mod/BIM/importers/exportIFC.py

@@ -111,7 +111,7 @@ def getPreferences():
     import ifcopenshell
 
     if FreeCAD.GuiUp and params.get_param_arch("ifcShowDialog"):
-        FreeCADGui.showPreferences("Import-Export", 1)
+        FreeCADGui.showPreferencesByName("Import-Export", ":/ui/preferences-ifc-export.ui")
     ifcunit = params.get_param_arch("ifcUnit")
 
     # Factor to multiply the dimension in millimeters

src/Mod/BIM/importers/importIFCHelper.py

@@ -84,7 +84,7 @@ def getPreferences():
         3 = One compound per storey
     """
     if FreeCAD.GuiUp and params.get_param_arch("ifcShowDialog"):
-        Gui.showPreferences("Import-Export", 0)
+        Gui.showPreferencesByName("Import-Export", ":/ui/preferences-ifc.ui")
 
     preferences = {
         'DEBUG': params.get_param_arch("ifcDebug"),

src/Mod/Draft/importDXF.py

@@ -4148,7 +4148,7 @@ def readPreferences():
     """
     # reading parameters
     if gui and params.get_param("dxfShowDialog"):
-        FreeCADGui.showPreferences("Import-Export", 3)
+        FreeCADGui.showPreferencesByName("Import-Export", ":/ui/preferences-dxf.ui")
     global dxfCreatePart, dxfCreateDraft, dxfCreateSketch
     global dxfDiscretizeCurves, dxfStarBlocks
     global dxfMakeBlocks, dxfJoin, dxfRenderPolylineWidth