For best practice, your exterior should be animated using helpers as skeletons, and the decals should be parented to these skeletons to move with them.
Then, you should export the livery with the entire skeleton/animation node.armature hirearchy included but without animations enabled and ensure 'export as submodel" and unique IDs are enabled for export of the livery.
Note that unique IDs should also be enabled for the base model you’re merging to.
As for decals which are on a surface with wing flex, they need to be wrapped and skinned to the existing wingflex and exported as I’ve mentioned above.
I’m not too sure about the Blender plug-in… although it might work without the export as submodel option if it doesn’t exist, as long as animations are not being exported on the livery export.
The “export as submodel” option is not available in Blender because it’s not needed. In 3dsmax we can skin any mesh on any objects. In Blender the meshs need to be parented to the armature, if you set up your rig and your scene correctly you will get the correct result for the “submodel option” without ticking anything.