I think and I want to emphasise that as I haven't checked - that there is a service where you pay a relatively small fee per month and you get access to all your e-cards as long as a host of other benefits. If these benefits are useful or not will depend on you as a person. And I'll let someone who is more active with padi say what they are and if it's even online yet.
I'd also point out - that you don't need all your cards. When I was working in a nice tropical location I didn't really care about seeing your open water card if you had AOW. If you have a tech50 card that will cover absolutely everything apart from self-reliant. So just take the tech50 (or have e-card version) and don't worry about the rest.
Well, it should be that way, but not always is. (I don't have a Tech 50 card BTW, it was an example to make the point).
Just last week at Rainbow Reef, the Solo (SDI) card I had on me would not get me on one of their boats for a deeper than shallow dive. So I pulled out the other card I had on me, a PADI Fundamentals in Tech card. Admittedly an odd one being shy of tech 40 and more than Intro... but it got me on there with a Padi#, AOW is a prerequisite, I have that with PADI, yet the shop employee could or would not be able to arrive at that I have e.g. valid PADI AOW cert...
I don't know why that is, but doesn't punching in one valid cert for a diver show all valid certs for that diver at least with that organisation? It should be that way..., but if RR can't or won't do it, who can / will?
So, bringing a higher card that requires the specific requested lower card as a prerequisite did not work here.
Hence I say it would be nicer if your latest card also showed all your prior certs with that organisation, so that you indeed can travel with one card (per cert. org.)
Luckily I had my other certs printed on paper, front and back (just a print of the scanned cards, not doctored), got that from the car and then that worked. Go figure... but I guess the actual AOW cert. number had to be inputted somewhere.