I am 30 and I find this hidden scrollbar fad (aka try-to-swipe-every-screen) really frustrating, am I already so old that UX designers should build special accessibility settings for me?

Sure, when I see younger people trying some new GUI they basically touch and swipe everything to discover hidden options and functionalities, because someone decided that a flat rectangle looked "cooler" than a button, or that a greyed out textbox looked more "modern" than a standard white one... but isn't this just bad design? what happened with make things as simple as possible, but not simpler and don't make me think?

Or the "shake to undo" in Notes on iOS that is totally undiscoverable. Also, three fingers gestures, 4 key keyboard shortcuts and ton of UI that changes when alt is pressed, Apple OS are actually harder to use than Windows in some respect.

windows generally had better default keyboard shortcuts than macOS, because many multi-key shortcuts could still be done one-handed (e.g., mash 2 keys with thumb), and shortcuts were better grouped somehow. the specifics escape me now, but i still miss the higher efficiency of windows shortcuts (which i haven't used regularly in over 10 years).

Shake to undo applies to all text boxes on iOS. But I don't blame you if you didn't know that, I only knew about it from the iPhone OS 3(?) keynote that introduced it!

Can you turn this off? I am asking because using an iPhone unlocked while cycling is activating this great feature regularly.

Go to Settings, scroll to the very top (beyond what shows as the top when you first open it). There's a search field (this is in a lot of other "list" styled interfaces like contacts as well). Type "undo" into the field. It'll bring up the location in settings to disable "shake to undo".

It's under the Accessibility settings if you want to just browse around for it.

Awesome, thank you very much

I'm gonna be the jerk who says you really shouldn't be using your phone while cycling.

navigation/gps? workout app? whats the difference between a workout app on my iphone compared to a dedicated device (e.g. garmin edge) in terms of safety?

You shouldn't be actively using, interacting with, and providing manual input to your device (be it a phone, garmin edge, or anything else) while cycling. An occasional glance at a navigation app (on a screen that is held by something other than your hand - a clip, stand, etc.) is probably fine - but taking your hand off a handlebar long enough to hold a device, and taking your concentration off your path long enough to interact with it, is asking for trouble.

quite a few assumptions here.

a) the shaking feature turns on even if i don't type anything just by the virtue of the phone being active (shaking can mean 'undo', not just 'undo typing')

b) i have it mounted on a quadlock on my handle bar, no holding whatsoever.

c) i take the risk of asking for trouble while cycling on a cycling path with no other cyclists near me (within, say, 300m). I am not cycling between 2 double decker buses while texting...

I'll grant you a) and b), but not the last one:

take the risk of asking for trouble while cycling on a cycling path with no other cyclists near me (within, say, 300m).

You don't know. If you start looking at your screen and you are moving, you are a danger to others. I don't care what happens to you, but I care that you don't hurt others. And you may.

If there is such a great risk doing that, do you not think that sharing the road with a car would be even riskier?

I.e. if there is no trust i can glance at a screen when i am on a cycling path with nobody around without injuring someone else, how can I be trusted while sharing the road with cars/buses/trams?

Well, I actually learnt about it years ago then forgot it. So, not only its impossible to find, it’s also easy to forget because no visual clues remind it.

I've been thinking about adding this to the app I'm working on, as a sort of UI hint. Just something real subtle at each edge that is scrollable, to signal the user that they can scroll in that direction (maybe a transparent animated chevron or something).

It definitely does feel like something the browser should handle though. Having to work on stuff like that instead of actual functionality is painful, especially for startups that are trying to iterate fast.