Currently the Secure feature only prevents you from deleting the lion, but still lets you put them up for Trade. I suggest an additional button (additional in case people would like to secure lions they're putting up for trade etc) that also prevents them from showing up in Trade creation in the same way roles for lionesses do. This way you don't have to give a role to a lioness to keep it from showing up, and you will also have a way to keep your submales from showing there. Helps with decluttering and prevents you from accidentally clicking on a wrong lion you absolutely don't want to lose!