I would suggest creating a String-Text map and getting the corresponding text on demand:
Of course you will have to enter each level manually in the map but allows for a lot of customization.
If you have some sort of naming convention @SupportiveEntity’s solution is better but if your levels are unorganized (or you suspect that you can’t enforce a naming convention, or the names contain special characters that you don’t want in your strings) adding pairs of level - name would be the way to go.
Using maps would allow you to later replace the Text part of the map with a struct that contains much more information for the level (like images, descriptions etc.)