It took some time until we implemented assignment of Custom Shortcuts from within the KeyRocket Shortcut Browser. The feature is now available in our frontier version and will be released for all users in about one week.
1. Open the Shortcut Browser by pressing Win+Shift+K
2. Search for the action you want to assign
3. Press the wrench to assign a shortcut
4. Press the shortcut and finish with Enter
5. Here you go: Your custom shortcut