Man, I really, really wish the writers had the foresight and carefulness in their writing to come up with some acceptable phlebotinum justifying why transporter clones and other various transporter transformations not just don't, but indeed can't happen.
I get that it makes for some plotlines, but it also makes for so much idiotic fridge logic. Like "why don't they save a pattern buffer copy of EVERY away team in case of emergency" or "why isn't the federation using a volunteer clone army for military engagements" or indeed what we here.
Or even "why isn't federation surgery just loading someone into the transporter buffer then editing their XML to fix the injury".
And don't even get me started by the wasted potential of holography, especially during and post-Voyager.
Or at least DISCO had used its 31st century setting to explore sci-fi concepts around any of these ideas. Like full on Iain M Banks The Culture, restoring people from their most recent mind state back up.
...until you realize that even the Jem'Hadar won't do it. They had transporters, right? I could maybe buy that the Romulans, Cardassians, and Klingons would refuse to do it based on some combination of pride and honor, maybe. I could never buy that an organization like Section 31 wouldn't, though, or any number of the monster-of-the-week species.
I think a good part of the reason they never addressed this is that there's no good answer. Any answer that posits it to be impossible that I can think of comes with awkward connections to the idea of a 'soul' or some such nonsense that makes duplicates non-viable, which I'm sure they really didn't want to introduce.
After all, it's not like transporters were part of a well thought out extensively considered backstory when they were first introduced. As I understand it, the issue was they didn't have the budget to keep shooting shuttlecraft scenes in every episode, so they came up with a way they could get the characters to the planet without having to use a vehicle in most situations. This decision has had its upsides and downsides, but I think on the whole, it has created far more issues than it ever solved. This is far from the only plot point that has issues in order for story to work with transporters. And considering how often they encounter situations where the transporters don't work, from an in-universe perspective the technology seems...unwise...to use on exploratory vessels.
It's easy for me to say with no time pressure and having had years to think it over, but I think rapidly decaying memory integrity would solve that issue. Saying a person's data was large and complex and pushed even the limits of the technology would explain why they couldn't just digitize everybody. The computer can only hold one pattern at a time and/or it degrades quickly.
This same caveat could also create limit on the amount and complexity of matter that could be transported, as well as create drama around technological arms races to build better computers to transport more crew at a time giving an edge to boarding parties to one side of a war.
It was always my understanding, that people are stored digitally in the transporter buffer, so of course they could be stored there for extended periods of time.
That's also why I was surprised when people argued that you cant copy people with the teleporter. For me it always was a remote replicator
It's already established that transporters can edit someone's DNA, so that would be a way to prevent aging and treating genetic diseases. If you have a way to duplicate the buffers then you could make a backup for cases when someone dies from an accident at the cost of a few hours of memories.