Sometime I will have bones set to non-selectable for clarity.
However, occasionally I may need to revisit those bones and want them to be interactable temporarily.
e.g. Want to add Transform Constraint later on or other operation that need to select bones temporarily.
My suggestion is to have a shortcut key for quick access to those locked items.
For example, when holding down [Alt] key, bones (or attachments) will have the alternate state:
Item with "Select" unchecked will became selectable and
Item with "Select" checked will became unselectable.
The state is flipped temporary and will be restored once [Alt] is no longer pressing down.
This would allow users to select what was set to unselectable quickly without too much effort.
Otherwise, in current implementation, I need to find that bones in hierarchy and check their Select checkbox then do the work and finally uncheck the Select checkbox again, which is quite lot of work compared to just holding down a key.