FBXImportMode -v [exmerge|add|merge;]
This command has three possible states:
Merges the imported FBX file to the current scene in the following way:
Nodes of the same name and nature have only their animation curve replaced. No new nodes are created. This command is the same as the Update animation option in the plug-in UI.
Adds the content to the current scene content. This command is the same as the Add option in the plug-in UI.
Merges the imported FBX file to the current scene in the following way: any node without its equivalent in the scene is created. Nodes with the same name but not of the same nature, for example, sphere and bone, are replaced. Nodes with the same name and nature only have their animation replaced. This command is the same as the Add and Update animation in the UI