Custom actions work with VoiceOver, Switch Control and Full Keyboard Access. They also do for Voice Control. You can say "Show actions for <item name/number>", and an action sheet with all options, numbered, will be presented to the user.
For some use-cases, Voice Control users might not feel it is a big win. Navigation is not as big of an issue, and interacting with custom actions might be a bit trickier than with "exposed" buttons. But lots of times seems a fair compromise.
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Grouping elements when it makes sense can make a huge impact on easing navigation with some assistive technologies like VoiceOver, Switch Control, or Full Keyboard Access. It also helps on reducing redundancy.
Accessibility values are about state. Using them appropriately will make the experience better for Voice Control users. Think of a repeat button (values could be: off, one or all songs) or a notifications tab (value could be: x new items). For more on accessibility values, check out this fantastic blog post from @MobileA11y with info on the APIs (UIKit, SwiftUI), accessibility attributed values, WCAG, or some more examples (text in a text field, value on a stepper or slider). https://mobilea11y.com/blog/accessibility-values/
Let's quickly remember a few of VoiceOver's most important gestures that will let you do some of the most basic actions including selection, interacting, navigating, and scrolling. And Apple has a great video: https://m.youtube.com/watch?v=qDm7GiKra28&feature=youtu.be
