diff --git a/addons/block_code/code_generation/block_definition.gd b/addons/block_code/code_generation/block_definition.gd
index 26ac9e70..b9a72e82 100644
--- a/addons/block_code/code_generation/block_definition.gd
+++ b/addons/block_code/code_generation/block_definition.gd
@@ -3,7 +3,7 @@ extends Resource
 
 const Types = preload("res://addons/block_code/types/types.gd")
 
-const FORMAT_STRING_PATTERN = "\\[(?<out_parameter>[^\\]]+)\\]|\\{(?<in_parameter>[^}]+)\\}|(?<label>[^\\{\\[]+)"
+const FORMAT_STRING_PATTERN = "\\[(?<out_parameter>[^\\]]+)\\]|\\{const (?<const_parameter>[^}]+)\\}|\\{(?!const )(?<in_parameter>[^}]+)\\}|(?<label>[^\\{\\[]+)"
 
 @export var name: StringName
 
@@ -102,6 +102,9 @@ static func parse_display_template(template_string: String):
 		elif regex_match.names.has("out_parameter"):
 			var parameter_string := regex_match.get_string("out_parameter")
 			items.append({"out_parameter": _parse_parameter_format(parameter_string)})
+		elif regex_match.names.has("const_parameter"):
+			var parameter_string := regex_match.get_string("const_parameter")
+			items.append({"const_parameter": _parse_parameter_format(parameter_string)})
 	return items
 
 
diff --git a/addons/block_code/ui/blocks/utilities/template_editor/template_editor.gd b/addons/block_code/ui/blocks/utilities/template_editor/template_editor.gd
index 6958114b..1d22c7bd 100644
--- a/addons/block_code/ui/blocks/utilities/template_editor/template_editor.gd
+++ b/addons/block_code/ui/blocks/utilities/template_editor/template_editor.gd
@@ -94,6 +94,8 @@ func _update_from_format_string():
 			_append_input_parameter(item.get("in_parameter"), match_id)
 		elif item.has("out_parameter"):
 			_append_output_parameter(item.get("out_parameter"), match_id)
+		elif item.has("const_parameter"):
+			_append_const_parameter(item.get("const_parameter"), match_id)
 		match_id += 1
 
 
@@ -104,7 +106,7 @@ func _append_label(label_format: String):
 	_container.add_child(label)
 
 
-func _append_input_parameter(parameter: Dictionary, id: int):
+func _append_input_parameter(parameter: Dictionary, id: int) -> ParameterInput:
 	var default_value = parameter_defaults.get(parameter["name"])
 
 	var parameter_input: ParameterInput = ParameterInputScene.instantiate()
@@ -126,6 +128,8 @@ func _append_input_parameter(parameter: Dictionary, id: int):
 	_container.add_child(parameter_input)
 	_parameter_inputs_by_name[parameter["name"]] = parameter_input
 
+	return parameter_input
+
 
 func _append_output_parameter(parameter: Dictionary, id: int):
 	var parameter_output: ParameterOutput
@@ -137,5 +141,12 @@ func _append_output_parameter(parameter: Dictionary, id: int):
 	_container.add_child(parameter_output)
 
 
+func _append_const_parameter(parameter: Dictionary, id: int):
+	# const_parameter is a kind of in_parameter with default value, but never
+	# changes value.
+	var parameter_const := _append_input_parameter(parameter, id)
+	parameter_const.visible = false
+
+
 func _on_parameter_input_drag_started(offset: Vector2):
 	drag_started.emit(offset)