How to disconnecting drawer slide?

I've made a mess of that vertical sliding cupboard which houses the dining table.  Suspect I'm not alone in putting the table in the wrong way round, resulting in the cupboard jamming after only opening a few inches.  Took a while of increasing violence with the awning pole to lever aside the jamming bit and open it fully...... and now repairs are needed to the cradle that holds the table.

But how to disconnect the slides so that the whole thing can be removed for fixing?  Manufacturer is Thomas Regout, but available videos etc don't appear to be for the slides fitted to our van.  

Anyone help?  And I am indeed not alone in making the original mistake?

Alan