Better explain advanced exports, script categories and groups (#5622)

* Make better explanation of advanced exports

Make better explanation of advanced GDScript exports because It was hard for me the first time I tried to do it it.

* Apply suggestions from code review

Co-authored-by: Hugo Locurcio <hugo.locurcio@hugo.pro>
Co-authored-by: Max Hilbrunner <mhilbrunner@users.noreply.github.com>

tutorials/scripting/gdscript/gdscript_exports.rst

@@ -236,28 +236,86 @@ described in :ref:`doc_accessing_data_or_logic_from_object`.
 .. warning:: The script must operate in the ``tool`` mode so the above methods
              can work from within the editor.
 
+Properties
+~~~~~~~~~~
+
+To understand how to better use the sections below, you should understand
+how to make properties with advanced exports.
+
+::
+
+    func _get_property_list():
+        var properties = [] 
+        # Same as "export(int) var my_property"
+        properties.append({
+            name = "my_property",
+            type = TYPE_INT
+        })
+        return properties
+
+* The ``_get_property_list()`` function gets called by the inspector. You
+  can override it for more advanced exports. You must return an ``Array``
+  with the contents of the properties for the function to work.
+
+* ``name`` is the name of the property
+
+* ``type`` is the type of the property from ``Variant.Type``.
+
+.. note:: The ``float`` type is called a real (``TYPE_REAL``) in the ``Variant.Type`` enum.
+
+Attaching variables to properties
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To attach variables to properties (allowing the value of the property to be used
+in scripts), you need to create a variable with the exact same name as the
+property or else you may need to override the 
+:ref:`_set() <class_Object_method__get_property_list>` and 
+:ref:`_get() <class_Object_method__get_property_list>` methods. Attaching
+a variable to to a property also gives you the ability to give it a default state.
+::
+
+
+    # This variable is determined by the function below.
+    # This variable acts just like a regular gdscript export.
+    var my_property = 5
+
+    func _get_property_list():
+        var properties = [] 
+        # Same as "export(int) var my_property"
+        properties.append({
+            name = "my_property",
+            type = TYPE_INT
+        })
+        return properties
+
 Adding script categories
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
 For better visual distinguishing of properties, a special script category can be
 embedded into the inspector to act as a separator. ``Script Variables`` is one
 example of a built-in category.
-
 ::
-
+    
     func _get_property_list():
         var properties = []
-        properties.append(
-            {
-                name = "Debug",
-                type = TYPE_NIL,
-                usage = PROPERTY_USAGE_CATEGORY | PROPERTY_USAGE_SCRIPT_VARIABLE
-            }
-        )
+        properties.append({
+            name = "Debug",
+            type = TYPE_NIL,
+            usage = PROPERTY_USAGE_CATEGORY | PROPERTY_USAGE_SCRIPT_VARIABLE
+        })
+        
+        # Example of adding a property to the script category
+        properties.append({
+            name = "Logging_Enabled",
+            type = TYPE_BOOL
+        })
         return properties
 
 * ``name`` is the name of a category to be added to the inspector;
 
+* Every following property added after the category definition will be a part
+  of the category. 
+
 * ``PROPERTY_USAGE_CATEGORY`` indicates that the property should be treated as a
   script category specifically, so the type ``TYPE_NIL`` can be ignored as it
   won't be actually used for the scripting logic, yet it must be defined anyway.
@@ -266,25 +324,39 @@ Grouping properties
 ~~~~~~~~~~~~~~~~~~~
 
 A list of properties with similar names can be grouped.
-
 ::
-
+    
     func _get_property_list():
         var properties = []
         properties.append({
-                name = "Rotate",
-                type = TYPE_NIL,
-                hint_string = "rotate_",
-                usage = PROPERTY_USAGE_GROUP | PROPERTY_USAGE_SCRIPT_VARIABLE
+            name = "Rotate",
+            type = TYPE_NIL,
+            hint_string = "rotate_",
+            usage = PROPERTY_USAGE_GROUP | PROPERTY_USAGE_SCRIPT_VARIABLE
+        })
+
+        # Example of adding to the group
+        properties.append({
+            name = "rotate_speed",
+            type = TYPE_REAL
+        })
+
+        # This property won't get added to the group 
+        # due to not having the "rotate_" prefix.
+        properties.append({
+            name = "trail_color",
+            type = TYPE_COLOR
         })
         return properties
 
 * ``name`` is the name of a group which is going to be displayed as collapsible
   list of properties;
 
-* every successive property added after the group property will be collapsed and
-  shortened as determined by the prefix defined via the ``hint_string`` key. For
-  instance, ``rotate_speed`` is going to be shortened to ``speed`` in this case.
+* Every following property added after the group property with the prefix
+  (which determined by ``hint_string``) will be shortened. For instance, 
+  ``rotate_speed`` is going to be shortened to ``speed`` in this case.
+  However, ``movement_speed`` won't be a part of the group and will not
+  be shortened.
 
 * ``PROPERTY_USAGE_GROUP`` indicates that the property should be treated as a
   script group specifically, so the type ``TYPE_NIL`` can be ignored as it