This feature allows site collection administrators to view all the columns of a list including hidden/read-only ones and gives column details such as the internal name, Guid, Type..
The feature also shows the CAML of the views attached to the given list and the event handlers associated to it.
On top of that, the features allows the site collection admin to switch the column state (from read-only to writeable, show in display form/not show, show in edit form/not show, show in newform/not show). These actions are not handled by the standard Sharepoint UIs.
To avoid unexpected mistakes, the operations described above are only available for custom columns (not hidden nor system columns)
Screenshots illustrating the solution
Feature at site collection level
After having activated the feature, you've got one extra link in the list's general settings
This link redirects you to a page where you can view/manage the list columns with contextual actions (changing according to the column status)
It also lists the views and events linked to the list