If you don’t need it to be an object, but a SkeletalMesh for example:
You can just set it to use the AttachParent in the user param settings in Niagara, then you parent/attach your NiagaraSystem within sequencer under your SkelMesh. Your Niagara system will then pickup the SkelMesh automatically.
Not quite sure why your event is not working, it should work as well. Try ticking the box to trigger the event in editor (even when not playing the game). The last step you can always take, is to create a blueprint with all this inside (your mesh, the sytem etc.) and then just trigger an event inside said blueprint, which does everything you need.
In some cases, AttachParent is OK.But the other is not.I need set it up in sequence by event.I don’t know why trigger couldn’t open sequence BP editor,so I use repeater to do this effect.