What happened to conveniently replacing component scripts in the inspector?

Image to illustrate:


Note that the “Limb” script is greyed out where I’ve circled it in red. In previous versions of Unity, you’d be able to drag a script that derived from Limb over this one and it would keep all the corresponding values set up. As far as I can tell, I’d have to remove “Limb” and readd my derived script to the object. This example is simple but for complex components re-setting up ALL the variables manually is a lot of time consuming work, not to mention external references that will be lost. Surely there’s another simple way to do this now?

EDIT: you can switch to debug mode and still do this, but why the change?

Not tried it myself but I remember someone saying that changing to Debug mode (from the drop-down next to the padlock icon at the top of the Inspector pane) re-enables the script field.