I think you probably need more dexterity (and grip strength) for minimal successful communication with a pen than with Morse code, especially if you wind up trying to do both without visual feedback.

The odds of those around you noticing is something you have some power over, if you're thinking about it ahead of time.

All true, but a pen still can be legibly used in at least some such situations. I've seen it done.

I'm not saying not to plan around Morse, just that it's a little early to assume there must be no other hope - and always too early to place much faith in being able to exert control over circumstances where, more or less definitionally, this is not a reasonable thing to expect.

That probably sounds scary. I can't help that. Dying is a scary topic, I imagine likely much more so for actually doing it, which I as yet have not. But I do know some things about how to handle fear, and one is that it helps a lot when that doesn't come by surprise - when you don't have to start totally from scratch to build what equanimity is available.

Less so than any one specific response, what I'd focus on trying to prepare for is that. You can't really know what tools you will have available in such a moment. You can't really know you will have any. Whatever there is, though, you'll have an easier time to recognize and use for being able to better see past that fear.

Probably my loved ones, or a subset thereof, would make the effort to learn. Otherwise there's software that can parse it (so people can read what I send) and software that can produce it (so people can type words and generate morse code I can receive via whatever means). :)