Allow 'virtual CDS/Protein' features to be overlaid without opening a CDS/Protein linked alignment

The ability to overlay cds or protein features from a linked alignment view is great, but its introduction comes at the expense of being able to 'Retrieve IDs' from Ensembl for a Uniprot sequence in order to bring sequence variants onto an already displayed view.

Whilst one could manually (or otherwise) transfer the virtual features via a sequence feature file onto the protein sequences, it would be nicer to be able to configure CDS features for a protein view *without* actually creating a CDS alignment, but just using existing CDS mappings for sequences.