The 'Position and Size' dialog has 2 checkboxes under the heading 'Protect' - position and size - which lock the size or position of an object, and i think is useful to have this in the context menu. This suggestion was primarily targetted as impress and draw, but calc and writer may also benefit from this as well.
A third item that should be included is aspect ratio, which in the dialog is labeled 'keep ratio'.
I think this needs to be re-evaluated
Adding A. Kainz to CC as he has experience in context menu changes.
As this kind of stuff is only available in the Position and Size dialog, I don't see an big with to have this checkboxes in the context menu.
As you can use Strg to fix the aspect ratio which is very common (inkscape, ...) I would say close this bug as wfm.