How to Backup Customized Keyboard Shortcuts on macOS?

Yes, they are backed up with Time Machine. You can test this yourself. Create a new test account and add some keyboard shortcuts in that account. Let Time Machine update your backup and delete the test account completely. Then use Migration Assistant to restore the deleted account fryhe backup.

Use Time Machine, the built-in backup feature of your Mac, to automatically back up your personal data, including apps, music, photos, email, and documents. 

https://support.apple.com/en-us/HT201250

Ocsprey wrote:

Thanks for confirming - I’d still like to find another way to avoid having to purchase an external drive for the backup. I’m wondering if I can do something like utilize a configuration profile? Please let me know if there’s another way - meantime I’ve marked this as solved.

Searching a bit about this, it appears that they are stored in a few different places:

for each application, in its plist file - e.g ~/Library/Preferences/com.safari.plist

for Services, they are in  ~/Library/Preferences/pbs.plist

and for global shortcuts in ~/Library/Preferences/.GlobalPreferences.plist

If you care about your data you should have a backup. As the old saying goes: there are two types of drives, the ones that failed amd the ones that are going to fail.

Everybody should have a backup strategy. Time Machine makes it so easy.

Since you worry about losing your carefully set shortcuts, more so you should be concerned with protecting your documents, photos, etc. Most of those may me irretrievably lost if your drive dies, or your mac is stolen. There are alternatives to backing up to a disk. You may opt for an online solution, but please do have a backup.