Good point by MK - Trik-l-start needs a charge source on the coach side such as plugging the RV into shore power, generator or solar.
You can use a temporary jumper cable to connect those same outer posts to put some charge from the house side to the chassis side if stranded. I'd let it charge or equalize with the house battery a bit then remove the jumper wire for the first try at starting the engine. RT's from then had 30A or 50A breakers.
I've used a short jumper on the isolator to maintain the chassis battery when plugged in. The problem with any non-automatic method is that you can forget to remove it. A note attached to the steering wheel helps with remembering. You can also forget to connect it.
Voltage through that type of isolator (from the alternator / middle post) drops as much as 0.7V so 14.4V drops to 13.7V. Neither the house side nor chassis get to see the sought after 14.4V recommended for charging lead acid batteries so they could fail prematurely if never fully charged.
An Automatic Charging Relay (ACR) - https://www.bluesea.com/articles/1366
- gets rid of that large voltage drop so the batteries get to see closer to recommended charge voltage. I use a similar device on my van now.