grouping in rhino is a very weak feature - i recommend to use nested layer-structures to organise a complex document.
i use grouping for very very few workflows - one is to organise curves for nesting as some dxf-based nesting / CAM software need grouping to identify curves that belong together - for example a wooden board (rectangle) with a drill-hole (circle).
i would claim that as soon as you need nested groups in rhino, you should re-thing the approach you structure the document (in rhino) - this might be confusing especially with the background of other programs where grouping and layers mean more or less the same.
If McNeel wants to improve grouping, a interface similar to layer-panel for groups would be nice.
or all group-names could at least be displayed in the object-properties.
with scripting (rhinoscript, phyton, rhinocommon) it is possible to remove an object from a single or from all groups.
hope this helps - kind regards -tom