First, all the wax needs to come off. Finishes wi;; not adhere to wax.

If you can get all the wax off, you have two choices. Paint and exterior varnish(spar varnish)

A #4 or #5(number depends on manufacturer) deep tint base paint with no tint added will dry clear. Paint with UV additives is the best outdoor protectant.

Spar varnish is the second choice. It does sometimes need periodic touchup or recoating, depending on exposure.

Spar varnish sounds like exactly what I need - I don't want to paint it because I would lose all the character of the wood with wormholes, etc.

Is this a DIYer could do with no furniture refinishing experience or do you need any particular technique to do it well?

Make sure to finish both sides of the table top or it will warp badly.

The paint I mentioned dries clear---that does not cover the character, it lets the wood grain show.

But, if you want the hassle of renewing the finish(samding/reapplying) every several years, use the varnish.

Will the table actually be in the elements inside the screen porch? If not, why not just continue to use the wax finish?