"Locked" column in the material list of Manage Materials can not be lengthened.
This was a design decision made so that the "Locked" column would not take up
too much screen real estate when the column only displays an icon.
The common NX UI tools allow a column size to be locked which what was done.
If left unlocked then the column would automatically resize to the column label
of "Locked" (or equivalent in other languages) and that was deemed too wide.