Add multi-select and ensure it works for toggling the visiblity of multiple muscles

[tgeijten]

For models with many muscle lines, I often wish to show/hide a large groups of muscles in order to reveal underlying muscles. It seems I can only hide one muscle at a time though. My ideal workflow would be:

1. Select multiple muscles in the navigator, by holding Control or Shift while left clicking
2. Right click -> Display -> Show/Hide

[adamkewley]

Hi,

This is a very good suggestion and something I'd like to do. The thing holding it up right now is that the current internal API design assumes one thing is selected (e.g. there's something like getSelected in the UI's datamodels) and that really needs to be ripped up and redesigned.

It'll take time because certain widgets (e.g. the property editor) will then need to be fiddled a bit to ensure that they're ready to editing multiple components at once!