So I have noticed on a lot of newer items added to castle story over the years like animals, new buildings flowers and items from events that we can place in our kingdoms no longer have the option to sell or essentially delete the items from our games since the button is now faded out
unlike on old decorations animals buildings etc we still have the option to get rid of.
it is not just event items as I have noticed even on permanent ones we can still buy in the store dont have the option either to “sell” it after purchase and placed into the kingdom.
So i suggest this option is reinstated since it does have a warning system in place for those who might say well what if I accidentally delete the wrong items. It will definitely help clear out old inventory especially of duplicate items that we no longer want remaining from events or quest lines or even having bought one too many.

edit to add I am only talking about the option on things that are placeable in our kingdoms and not inventory cards of items collected to do upgrades in various events that cannot be placed since many have already suggested solutions for that as well..