8 files changed, 30 insertions, 12 deletions
diff --git a/release/scripts/modules/rna_prop_ui.py b/release/scripts/modules/rna_prop_ui.py
index 12b423d637b..9660a2d29be 100644
--- a/release/scripts/modules/rna_prop_ui.py
+++ b/release/scripts/modules/rna_prop_ui.py
@@ -280,6 +280,7 @@ class PropertyPanel:
     """
     bl_label = "Custom Properties"
     bl_options = {'DEFAULT_CLOSED'}
+    bl_order = 1000 # Order panel after all others
 
     @classmethod
     def poll(cls, context):
diff --git a/release/scripts/startup/bl_ui/properties_freestyle.py b/release/scripts/startup/bl_ui/properties_freestyle.py
index 095bd182ad4..7ddfb298a1b 100644
--- a/release/scripts/startup/bl_ui/properties_freestyle.py
+++ b/release/scripts/startup/bl_ui/properties_freestyle.py
@@ -39,6 +39,7 @@ class RenderFreestyleButtonsPanel:
 class RENDER_PT_freestyle(RenderFreestyleButtonsPanel, Panel):
     bl_label = "Freestyle"
     bl_options = {'DEFAULT_CLOSED'}
+    bl_order = 10
     COMPAT_ENGINES = {'BLENDER_RENDER', 'BLENDER_EEVEE'}
 
     def draw_header(self, context):
@@ -66,6 +67,7 @@ class ViewLayerFreestyleButtonsPanel:
     bl_space_type = 'PROPERTIES'
     bl_region_type = 'WINDOW'
     bl_context = "view_layer"
+    bl_order = 10
     # COMPAT_ENGINES must be defined in each subclass, external engines can add themselves here
 
     @classmethod
diff --git a/release/scripts/startup/bl_ui/properties_material.py b/release/scripts/startup/bl_ui/properties_material.py
index dde67e27f37..4eb33efd151 100644
--- a/release/scripts/startup/bl_ui/properties_material.py
+++ b/release/scripts/startup/bl_ui/properties_material.py
@@ -233,6 +233,7 @@ class MATERIAL_PT_viewport(MaterialButtonsPanel, Panel):
     bl_label = "Viewport Display"
     bl_context = "material"
     bl_options = {'DEFAULT_CLOSED'}
+    bl_order = 10
 
     @classmethod
     def poll(cls, context):
diff --git a/release/scripts/startup/bl_ui/properties_object.py b/release/scripts/startup/bl_ui/properties_object.py
index 3265366a2f9..6a938b40c2e 100644
--- a/release/scripts/startup/bl_ui/properties_object.py
+++ b/release/scripts/startup/bl_ui/properties_object.py
@@ -212,6 +212,7 @@ class OBJECT_PT_collections(ObjectButtonsPanel, Panel):
 class OBJECT_PT_display(ObjectButtonsPanel, Panel):
     bl_label = "Viewport Display"
     bl_options = {'DEFAULT_CLOSED'}
+    bl_order = 10
 
     def draw(self, context):
         layout = self.layout
diff --git a/release/scripts/startup/bl_ui/properties_render.py b/release/scripts/startup/bl_ui/properties_render.py
index 45a492c0ff7..db017ddfdc5 100644
--- a/release/scripts/startup/bl_ui/properties_render.py
+++ b/release/scripts/startup/bl_ui/properties_render.py
@@ -63,6 +63,7 @@ class RENDER_PT_context(Panel):
 class RENDER_PT_color_management(RenderButtonsPanel, Panel):
     bl_label = "Color Management"
     bl_options = {'DEFAULT_CLOSED'}
+    bl_order = 100
     COMPAT_ENGINES = {'BLENDER_RENDER', 'BLENDER_EEVEE', 'BLENDER_WORKBENCH'}
 
     def draw(self, context):
diff --git a/release/scripts/startup/bl_ui/properties_world.py b/release/scripts/startup/bl_ui/properties_world.py
index d059c2d2e4d..705be66ecc1 100644
--- a/release/scripts/startup/bl_ui/properties_world.py
+++ b/release/scripts/startup/bl_ui/properties_world.py
@@ -152,6 +152,7 @@ class EEVEE_WORLD_PT_volume(WorldButtonsPanel, Panel):
 class WORLD_PT_viewport_display(WorldButtonsPanel, Panel):
     bl_label = "Viewport Display"
     bl_options = {'DEFAULT_CLOSED'}
+    bl_order = 10
 
     @classmethod
     def poll(cls, context):
diff --git a/source/blender/blenkernel/BKE_screen.h b/source/blender/blenkernel/BKE_screen.h
index 167fce4406c..dcf6d6c3907 100644
--- a/source/blender/blenkernel/BKE_screen.h
+++ b/source/blender/blenkernel/BKE_screen.h
@@ -208,6 +208,7 @@ typedef struct PanelType {
   short region_type;
   /* For popovers, 0 for default. */
   int ui_units_x;
+  int order;
 
   int flag;
 
diff --git a/source/blender/makesrna/intern/rna_ui.c b/source/blender/makesrna/intern/rna_ui.c
index faa16f4f146..0dbafbde71c 100644
--- a/source/blender/makesrna/intern/rna_ui.c
+++ b/source/blender/makesrna/intern/rna_ui.c
@@ -317,19 +317,21 @@ static StructRNA *rna_Panel_register(Main *bmain,
   pt->draw_header = (have_function[2]) ? panel_draw_header : NULL;
   pt->draw_header_preset = (have_function[3]) ? panel_draw_header_preset : NULL;
 
-  /* XXX use "no header" flag for some ordering of panels until we have real panel ordering */
-  if (pt->flag & PNL_NO_HEADER) {
-    PanelType *pth = art->paneltypes.first;
-    while (pth && pth->flag & PNL_NO_HEADER)
-      pth = pth->next;
-
-    if (pth)
-      BLI_insertlinkbefore(&art->paneltypes, pth, pt);
-    else
-      BLI_addtail(&art->paneltypes, pt);
+  /* Find position to insert panel based on order. */
+  PanelType *pt_iter = art->paneltypes.last;
+
+  for (; pt_iter; pt_iter = pt_iter->prev) {
+    /* No header has priority. */
+    if ((pt->flag & PNL_NO_HEADER) && !(pt_iter->flag & PNL_NO_HEADER)) {
+      continue;
+    }
+    if (pt_iter->order <= pt->order) {
+      break;
+    }
   }
-  else
-    BLI_addtail(&art->paneltypes, pt);
+
+  /* Insert into list. */
+  BLI_insertlinkafter(&art->paneltypes, pt_iter, pt);
 
   if (parent) {
     pt->parent = parent;
@@ -1347,6 +1349,14 @@ static void rna_def_panel(BlenderRNA *brna)
   RNA_def_property_flag(prop, PROP_REGISTER_OPTIONAL);
   RNA_def_property_ui_text(prop, "Units X", "When set, defines popup panel width");
 
+  prop = RNA_def_property(srna, "bl_order", PROP_INT, PROP_UNSIGNED);
+  RNA_def_property_int_sdna(prop, NULL, "type->order");
+  RNA_def_property_flag(prop, PROP_REGISTER_OPTIONAL);
+  RNA_def_property_ui_text(
+      prop,
+      "Order",
+      "Panels with lower numbers are default ordered before panels with higher numbers");
+
   prop = RNA_def_property(srna, "use_pin", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "flag", PNL_PIN);
   RNA_def_property_ui_text(prop, "Pin", "");