Started prototyping flexible UI layout

addons/flexible_layout/flexible_dragger.gd

@@ -0,0 +1,31 @@
+extends Control
+
+
+var dragging : bool = false
+var flex_split
+var dragger_index : int
+var vertical : bool
+
+func _init():
+	set_meta("flexlayout", true)
+
+func _draw():
+	draw_rect(Rect2(Vector2(0, 0), size), Color(1, 1, 0))
+
+func set_split(s, i : int, v : bool):
+	flex_split = s
+	dragger_index = i
+	vertical = v
+
+func _on_gui_input(event):
+	if event is InputEventMouseButton:
+		if event.button_index == MOUSE_BUTTON_LEFT:
+			dragging = event.pressed
+	elif event is InputEventMouseMotion:
+		if dragging:
+			if vertical:
+				position.y += event.position.y-5
+				flex_split.drag(dragger_index, position.y)
+			else:
+				position.x += event.position.x-5
+				flex_split.drag(dragger_index, position.x)

addons/flexible_layout/flexible_dragger.tscn

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+[gd_scene load_steps=2 format=3 uid="uid://cucx3oayvvxhu"]
+
+[ext_resource type="Script" path="res://addons/flexible_layout/flexible_dragger.gd" id="1_3i5mx"]
+
+[node name="Dragger" type="Control"]
+custom_minimum_size = Vector2(10, 10)
+layout_mode = 3
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_3i5mx")
+
+[connection signal="gui_input" from="." to="." method="_on_gui_input"]