I just installed a new converter on my '98 Casita. It has a 30A breaker that brings in the power to the AC distribution bus. There are several 15A breakers on this bus and one is for the DC converter/charger. Opening this would shut down the converter. The second way is there is a 30A fuse on the DC side which removing it disconnects the battery. Do you have your converter's manual, or can you get a copy on-line? It should show you how to disconnect the battery.
The reason I replaced my converter is that I purchased an AGM battery which requires at least a 3 step charger. The old converter was only a one step. I also added drawer slides to the battery box to allow the battery to easily be rolled out for inspection and maintenance. You're right it is a bit of a trick to position the wires so they will come out with the battery, not snag or risk shorting out, but it is do-able. I also added a disconnect switch just inside the battery door to open the battery circuit. The only problem is the weight
of the battery would quickly snap off the drawer if not supported when the battery is pulled out. I use a piece of wood as a leg to support it.