I recall seeing somewhere on this forum a picture of a stem that was adjustable. It basically allowed you to move the stem up or down from a pivot point and lock it in.

I'm not sure how stable it might be but I'm interested to see if it might help me dial in what I need instead fo committing to a particular fixed stem.

Thanks.

And your question is?
Yes, there are adjustable stems. Both for quill stems and aheadset stems.
Most are angle-only. A select few are angle-and-reach.
They are generally seen as OK for fit testing purposes, but to be replaced ASAP with a fixed stem offering the desired rise and reach.
Me, I’m not so categorical.
Sure, I realize they’re heavier than a fixed stem.
And I’ve seen a couple that have developed an annoying play during use.
But IME, the weight penalty overall isn’t much to moan about.
And - If tightened correctly after adjustment - you need to put out some serious watts before the flex coming from being adjustable becomes a valid issue.

When I bought my last bike, I purchased some cheap stems and tried a few, along with different stem spacers to get it right. Then when I had it right, I bought a proper stem (one I'd be happy with) and then cut down the extra tubing afterwards. I kind of knew in which direction I'd go.

If I was wanting to see what angle was best for me, but knew what reach, I'd buy the cheapest adjustable and figure what angle I wanted, then buy a regular stem. I want something solid when it comes to steering. IF I was to use an adjustable (but don't think I would), from what I've read, the only one I might consider would be one from Ritchey: https://www.jensonusa.com/Ritchey-4-...20Group%20%231 The two bolt design for adjustment would seem to be much better than a single bolt.

I've used an adjustable stem, previously. A Ritchey 4-axis adjustable (click @ Ritcheylogic.com); this one's an example of a stem for the AheadSet standard. Works fine. Take it apart, lock it down, and it's set. It's got big splines inside the unit that aren't going anywhere once you tighten the adjustment screw. Very solid. Indistinguishable from a typical non-adjustable stem, function-wise, other than it adjusts in angle. There are less-expensive adjustable stems made, but the Ritchey is a well-designed one.

As others have said, similar units are available out there for quill-type stems.

I've used it and kept it, in some cases. And I've used it to dial-in the fit, then swapped it for the correct stem (angle and length). Works fine, either way.

Am currently building-up a bike that has an uncut steerer on the fork, which extends a good foot above the head tube. Using numerous spacers, I'm able to raise the height of the existing stem to the height where the bars will result in "perfect" hand position. Once I've determined the right spot (for the hands), I'll get a stem with the appropriate angle and length (likely, shorter and much steeper), then cut off the "excess" from the steerer tube. (Right now, the length of the steerer tube is ludicrously tall, but that's only for testing/fitting purposes and temporary.)

This is perfect. I swapped out the seat that works better. The current stem is only about 5 degrees so the Richey allows more than that -- and enough to likely get the fit I need. Thank you!

IIRC, the Ritchey can adjust to about a 55 degree angle. You just take off stem's "neck" from the stem's base, then reinstall so the splines lock up at a different angle, then tighten the bolt. Easily done, assuming the length of your cables allow that range of motion. Works well. Isn't going anywhere, once you reassemble and tighten down.