Transparency slider disappears when a group layer is excluded from the Layer List

Hi,

I have a group layer in a web map used by VertiGIS Studio Web. The group layer and its child layers come from a map service. The layers are visible in the map.  

When the group layer is included in the Layer List, a transparency slider is available, see screenshot below.

However, when I configure the group layer so that it is not included in the Layer List component, the transparency slider also disappears.

I would like to hide the group-layer entry from the Layer List while still allowing users to adjust the transparency of the visible child layer(s).

Is this behaviour by design, or is it a bug?

If it is by design, is there a recommended way to:

• hide the parent group layer from the Layer List;
• keep its child layers visible in the Layer List; and
• retain a transparency slider for the child layers or for the group as a whole?

Environment:

VertiGIS Studio Web version: 5.40.0
ArcGIS Enterprise: 11.3