Update audio track volume slider

Views/Timeline.tscn

@@ -2,8 +2,7 @@
 
 [ext_resource type="Script" path="res://Scripts/Timeline.gd" id="1_h2mev"]
 
-[node name="Timeline" type="Control"]
-layout_mode = 3
+[node name="Timeline" type="Container"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
@@ -14,23 +13,6 @@ script = ExtResource("1_h2mev")
 end_time = 4000.0
 
 [node name="ScrollBar" type="HScrollBar" parent="."]
+visible = false
 custom_minimum_size = Vector2(0, 20)
-layout_mode = 1
-anchors_preset = -1
-anchor_top = 0.97
-anchor_right = 1.0
-anchor_bottom = 1.0
-offset_top = 24.4
-grow_horizontal = 2
-grow_vertical = 0
-
-[node name="Panel" type="Panel" parent="."]
-modulate = Color(0.674815, 0.674815, 0.674814, 1)
-show_behind_parent = true
-layout_mode = 1
-anchors_preset = 15
-anchor_right = 1.0
-anchor_bottom = 1.0
-grow_horizontal = 2
-grow_vertical = 2
-mouse_filter = 2
+layout_mode = 2