Risa

The Riker example was just one of many wasn’t it? The “transporter clone” trope has been around since StarTrek: The Original Series when Captain Kirk was replicated by accident. As well as recent trek canon when Boimler was replicated on StarTrek: Lower Decks.

Kirk wasn't cloned, he was split into two different versions of himself that contained different parts of his personality/ego. A clone needs to be a copy, not a lower resolution version of the character. Also Boimler was re-created through the same fashion that Riker was. It also happened 20ish years after Voyager left for the Delta Quadrant.

From an in-universe perspective, given the numerous transporter accidents throughout Starfleet’s history, it would seem logical that Starfleet would invest resources into understanding these anomalies to prevent unintended duplications or other mishaps. Transporter technology is complex and interacts with a myriad of environmental conditions, which might explain why these accidents, while rare in the context of all transport operations, still happen occasionally.

They do. Starfleets whole thing is exploration and study. During the episodes where there have been clones you see a vast amount of information that's uncovered. Testing is done to see what happened and how to prevent it from happening again in the future.

Voyager could have taken the next steps and introduced a new level of control over the technology by relying on Starfleet, had it thoroughly investigated and understood these incidents. I don’t see why they might not have developed protocols or technologies to recreate such anomalies intentionally. This could have provided Captain Janeway with an additional solution to the Tuvix dilemma.

This doesn't make sense. You're asking Voyager, who is tens of thousands of lightyears from known space, to somehow recreate an anomaly. They do not have the level of study of each planet that would be required to find a suitable testbed. They also do not have the time. They're looking for ways to get home. The anomalies they've stopped and encountered along the way (without being pushed into investigating by aliens) have been overwhelmingly to either further the goal of getting home faster or to supply the ship with necessities for the trip. Moreover, there's the fact that the transporter cloning incidents were pure anomalies. Just because Starfleet studied them and knows what happens does not mean that they're able to recreate it. We've seen numerous times that Starfleet can understand a phenomena but can't replicate it. You're asking way too much of a small science vessel stranded in the Delta Quadrant.

Also as for which to kill, that would of course be up to Tuvix - which without his consent this would be moot.

That's the pint I am trying to make. You will not get his consent. Ever. He doesn't want to die. Just because you clone someone doesn't mean that logically they're going to go "Oh, well I guess, I can die if it means that another version of me lives." He was acting on a survival instinct. He's not going to override that just because there's a clone. Which means you must still make the decision that Janeway made. You STILL MUST decide whether to kill Tuvix or let him live. Your cloning idea might be a nice idea but that's all it is. An idea. When put into practice it immediately falls apart because you're back to the same argument that was made at the start. Do you have the right to execute one man to save the lives of two others? The issue of the episode isn't "Tuvix is a unique lifeform and then must be saved". It's "Do you have the right to kill someone in order to save others?" If you add a transporter clone into that mix the question doesn't change.

The transporter clone option is a nice idea but that's all it is. An idea. There is no situation in which you can put it into practice and have it be a solution to the problem.