How does Nikon D3400 adjust the effect of camera shooting delayed video?

Shoot it directly. This machine can't shoot it. You can set interval shooting, and then use software to synthesize the delayed video.

How to set the interval shooting, zlzcyhu has answered very well, so I won't go into details.

If the camera can't be set up or there is no interval shooting, you must buy a multi-function wired releaser.