Using SM6-24 cubicles (e.g. IM cubicles), you still have an option to install "key interlock" option according to the interlock configuration needed.
Attached a few pages of SM6 catalog illustrating the idea of this interlock.
Note: for IM cubicles, for instance, you may use "A3 type" key interlock in order to prevent the closing of the earthing switch of your SM6 IM cubicle unless the line-side (i.e. cable side) switch is locked in "open" position, please also see the scheme of this locking in page (91) of attached pages