That won't change if you had a different dedicated key for "move one line down but don't send `enter` keycode". You'd still accidentally hit `enter` due to muscle memory.
After all, if you could get past muscle memory, you'd simply press Shift while hitting Enter.
This is useful if you're trying to type verbatim inside a block, it's less so if you have a strong muscle-memory to shift+enter and do so while in the code block and find yourself sending half a message.
I also use a mixture of teams, discord and slack, and while slack does allow for customisations, I'd always rather get used to defaults to avoid having to configure on every machine I use.
There isn't quite a consistent well agreed default for the behaviour across applications, and that too is a source of frustration.
So I've taken to typing up any long messages in a PM to myself, and then copying that out to my intended target once I'm ready.
There's a setting to turn that off so it behaves consistently. Or there was last time I used Slack.
But changing settings on platforms which I need to use across different computers and accounts is also cause for frustration, so I try to adapt to the defaults, no matter how frustrating.