After checking the mess I have in my garage/workshop I found a product I used some 12 yrs. ago to protect one of the entrance doors to my home. It is made here in Puerto Rico for our climate, and it's called Belle Wood Sealer & Finish. It comes in different stain colors and clear, I have the clear one. I used it then to protect an Imbuia Wood Door, the indoor side of the door has never been retouched, and it looks new, the outdoor side of the door gets full frontal sun from the West for about 6 hours every day for the last 12 yrs., I have only had to reapply once about 2 yrs. ago and it looks great.
So, I tried some on a small sheet of walnut veneer, and it looked very nice, no need to stain, no need to sand, just apply with a foam brush or stain pad or lint-free rag. After applying the first coat all it needs is 15-20 minutes to dry then you can give it a second coat. The product applies milky white, so you now that you have covered the whole surface, then it turns totally clear. It is a waterbase varnish, it has almost no odor, you can apply without gloves, dries super fast, and leaves a hard crystal clear non-yellowing protective finish without altering the color of the wood.
The manufacturer recommends you use a 220 Grit to sand prior to applying, but both times I have used this product I haven't had the need to sand. They also recommend to lightly sand with 320 Grit in-between coats and not to sand the last coat. Depending on how many coats you use, it goes from satin to high gloss just by applying more coats. I applied 2 coats without sanding, tomorrow I will lightly sand, and apply a 3rd coat, and leave it like that. The walnut veneer looks very nice without staining, just using this product (clear).
This is a very nice product that I had forgotten about, plus apparently it has a looooong shelf life, as it is about 10 yrs old and it still works perfectly.
The first pic is just when it started to turn from milky white to clear, the sheen is due to it being wet still. The second pic is two coats dried no sanding at all.