After setting up a corporate design in LibreOffice master slides the elements should stay locked in place and size if you lock them in the master.
If you lock them and then use them later you can drag around everything again. It seems almost impossible to set up a consistent, forced layout in Impress.
It would be nice if this would be possible.
Indeed locking the elements in the Masterslide does not lock them in the devirated new slides.
I think that would be a nice feature corporate designs another imho even more interesting solution for that kind of feature would be the possibility to lock templates with a password similar to the mechanism you can lock cells in Calc.