CURA-4461 Change sizes and theme colors for the separator

resources/qml/SidebarHeader.qml

@@ -323,8 +323,8 @@ Column
         anchors.horizontalCenter: parent.horizontalCenter
         visible: buildplateRow.visible
         width: parent.width - UM.Theme.getSize("sidebar_margin").width * 2
-        height: visible ? UM.Theme.getSize("sidebar_lining").height / 2 : 0
-        color: UM.Theme.getColor("sidebar_lining")
+        height: visible ? UM.Theme.getSize("sidebar_lining_thin").height / 2 : 0
+        color: UM.Theme.getColor("sidebar_lining_thin")
     }
 
     //Buildplate row

resources/themes/cura-dark/theme.json

@@ -43,6 +43,7 @@
         "sidebar_header_text_hover": [255, 255, 255, 255],
         "sidebar_header_text_inactive": [255, 255, 255, 127],
         "sidebar_lining": [31, 36, 39, 255],
+        "sidebar_lining_thin": [255, 255, 255, 30],
 
         "button": [39, 44, 48, 255],
         "button_hover": [39, 44, 48, 255],

resources/themes/cura-light/theme.json

@@ -91,6 +91,7 @@
         "sidebar_header_text_active": [255, 255, 255, 255],
         "sidebar_header_text_hover": [255, 255, 255, 255],
         "sidebar_lining": [245, 245, 245, 255],
+        "sidebar_lining_thin": [127, 127, 127, 255],
 
         "button": [31, 36, 39, 255],
         "button_hover": [68, 72, 75, 255],