I know this is more a quality of life thing for me because of browser issues which make interacting with creatures a bit tricky, but am certain some users would love to be able to utilise such a feature if it was available: Please can we have the option to lock all creatures in a 'group' from being traded, either by simply removing the 'send to duplicates' button from the actions at the base of the creature's 'card' or something similar. Removing the creature to the unsorted group would make them accessible for trading again (nice if you have genuine duplicates that you're happy to let go of at a later stage or have inadvertantly moved a duplicate there, or acquired a creature with the date/land/gender that you prefer and want to replace the existing group member)
I think it would be nice as a default setting, but with the option to toggle for people with less... acquisitive habits. (non collectors/hoarders) And/or to have each group set individually (at the clan settings page) again making it easy to deal with hoards as opposed to collections.
As it's tricky enough when moving them to the groups (it would also be more convenient if the move to group button is clearer and not the tiny little block it is now, as it is hard for visually troubled individuals and people not paying attention to click the right button) and accidentally clicking the send to duplicates group is a pain at the best of time
I don't think it should apply to the duplicates group though and given how this seems to be set up at the moment looks like it wouldn't be a big ask to code
I apologise if something similar has been suggested and I've missed it though too.