gistfile1.txt

import bpy
from bpy_extras.io_utils import ExportHelper
from bpy.types import Operator
from bpy.props import StringProperty

class SaveAsOperator(Operator, ExportHelper):
    """Open a file browser to specify a file to save"""
    bl_idname = "wm.save_as_file"
    bl_label = "Export FBX (sep. animations)"
    filename_ext = ".fbx"

    def execute(self, context):
        # Get the list of all actions
        actions = bpy.data.actions

        # Get the active object
        obj = bpy.context.active_object

        # Export mesh with no animations
        bpy.ops.better_export.fbx(filepath=self.filepath, my_fbx_version='FBX200900', use_animation=False, use_edge_crease=False)

        # Iterate through all actions
        for i, action in enumerate(actions):
            # Set the action to the active object
            obj.animation_data.action = action
            index = self.filepath.find('.fbx')
            output_line = self.filepath[:index] + f'@{action.name}' + self.filepath[index:]
            
            # Export singular animation
            bpy.ops.better_export.fbx(filepath=output_line, my_fbx_version='FBX200900', use_edge_crease=False)
        return {'FINISHED'}

# Register the operator
def register():
    bpy.utils.register_class(SaveAsOperator)

def unregister():
    bpy.utils.unregister_class(SaveAsOperator)

if __name__ == "__main__":
    register()
    
    # Launch the file browser immediately
    bpy.ops.wm.save_as_file('INVOKE_DEFAULT')