Disable the selected option instead of removing it from list

[raghavio]

When we select an option from the list it gets removed. It would be better to disable it so it can't be selected again instead of removing it. It messes up list and makes it look ugly if using it with groups.

[RolandHeath]

@Raghavpro An alternative approach to this feature might be to remove/hide groups if they are empty. That way, it wouldn't look ugly, and if you had a long list you wouldn't have to scroll through as much after selecting elements.
I'm not sure if that would suit your needs, but it could be worth considering.

[lohandus]

All options selected, without groups, breaks the layout too: