For things that can be added via popover - and repeat endings and repeat barlines are both things that can be added via popover - there generally aren’t direct shortcuts defined by default. If you’re lucky, the functions exist in the Key Commands list for you to assign your own shortcut. Don’t expect existing key commands to be defined, though.
For that matter, with a bit of backdoor JSON hackery it’s possible to define shortcuts for things that don’t exist in the Preferences > Key Commands dialog (see Dorico 3 - Keyboard shortcuts for microtonal accidentals? - #5 by pianoleo for instance). If you’re new to Dorico, though, try to get to grips with the popovers. They’re generally quick enough for most things.