You can change the default keyboard shortcuts, or even add new ones, in macOS System Preferences > Keyboard > Shortcuts following Apple's guide to Create keyboard shortcuts for apps on Mac.
The default keyboard shortcuts are listed below.
Reminders
| Postpone by 10 Minutes | ⌘= |
|
Postpone by 1 Hour |
⇧⌘= |
|
Postpone by 10 Minutes |
⌥⇧⌘= |
|
Mark Done |
⌘D |
|
Delete |
⌫ |
Timers
| Start/Stop | ⌘S |
| Reset | ⇧⌘S |
| Delete | ⌫ |
Switching Views
| Show/Hide Sidebar | ⌘0 |
| Show Reminders | ⌘1 |
| Show Timers | ⌘2 |
| Show Logbook | ⌘3 |
Others
| New Item | ⌘N |
| Sync Now | ⇧⌘R |
| Preferences | ⌘, (Command + Comma) |