You should be able to restore a deleted workout type by:
- tap on workout app
- then scroll down to the bottom and tap on "Add Workout"
- finally tap on a workout type in the list
and it will be added back to your workout list.
If not, the first (and simplest) thing to try if something isn’t working right is to restart your Apple Watch and its paired iPhone. If necessary (device not responding), try a forced restart. Both methods can be found here:
How to restart your Apple Watch - Apple Support
Restart your iPhone - Apple Support
If that doesn't help, the next steps would be to unpair and pair your watch again and restore from the backup just created. This should result in no loss of data. It deletes all temp and corrupted files and re-indexes the file system.
Unpair and erase your Apple Watch - Apple Support
Set up your Apple Watch - Apple Support
Then try again if they don't appear.