It depends on the knot, but if you put it on the wrong knot, it can make the connection weaker. This is especially true with coil-based knots like the uni and improved clinch. By design, the more pressure you put on them, the more tightly they should cinch. Adding glue to the wraps, however, will lock them in place, halting their ability to get any tighter through the day as you retrieve lures and fight fish. It’s much more common to see a dab of glue used on line-to-line connections than it is line to hook/lure/fly connections.