[Feature Request] Objects UI has a collapsed group containing non-explictly shown objects

[garywill]

import cadquery as cq

a=cq.xxxxxx .....
b=cq.xxxxxx .....
c=cq.xxxxxx .....

If we don't use show_object(), then a,b,c are shown in CQ-editor's Object UI.

If we use

show_object(c)

then a,b are ignored completely in CQ-editor.

Please add a group to Objects UI. It is collapsed by default. It contains a, b and those non-explictly shown objects which are set to invisible by default. User can manually enable object in that group to make a object visible.