dockge is very nice 
i setup all my dockers via jailmaker, so i’m less experienced doing it the truenas way via the ui. i didnt even touch that.
for jailmaker, dan updated the guide to install that for electric eel
so once jailmaker docker is installed, you can then install dockge. i did so login to jailmaker docker jail
in shell, jlmkr shell docker
i then cd to where my docker compose is located, then i do the docker compose up d to deploy the docker compose for my dockge. this installs dockge.
then i go to the web url to dockge. from this point onward you have the dockge UI. You can then deploy the rest of your docker containers through dockge ui. So it was only dockge that you had to install manually ^^;
in your dockge docker compose, you can specify where your docker stacks go.
so stacks is separated from the data folder.
stacks is where it archived your docker compose for each container.
the data folder is where your docker container configs go to.
So to back up your docker containers, simply go to truenas shell, do jlmkr stop docker
once it’s stopped, run the backup for the stacks and the data folder locations. To keep it simple though those are 2 separate folders, they are both located under the docker location i set. So i simply backup docker folder