The hulls of submodels within submodels cannot be moved independently

[maxneal]

To reproduce:

• Open hinch et al. example CellML model and select a submodel visualization.
• Double click the "membrane" submodel to expand its contents.
• Then double click the "CaRU" submodel

You cannot move the CaRU submodel hull independently of its parent "membrane" submodel hull Also, you cannot collapse the CaRU submodel hull without collapsing its parent "membrane" submodel hull