When you want to delete a label value, you need to clean up first all the element that was using this label value. When you have board with hundred of lines using this label value, it’s almost impossible to manage.
As an exemple, we regularly (every 3 months) want to adapt our current label value list (Add/Change/Remove) according company referentials. That means, we need to Go in each board using this lael value (we also use mirroring) and clean up each board before it start to be possible the value is no more grey.
Could you add a capability for administrator to delete or edit used label and to adapt automatically the line using it (with for example a pop-up warning saying : This lavel value is used, by doing this change you will remove/change all the component using this value)