Scribe training on chol-ha-moed

Is a scribe allowed to practice writing Torah, phylacteries and mezuzos on chol-ha-moed (intermediary days of a holiday)? The problem is that if I don’t practice on chol-ha-moed, my whole training will get delayed. Is it possible to permit it because it’s something that’s needed for fulfillment of a commandment? Or maybe it’s possible to permit it as something that’s going to be irretrievably lost (because I’m losing my ability to earn money as a result of a delay in training)?

Dear …!

It is prohibited to write for this purpose on chol-ha-moed.

If you are only practicing, this is not called “performing labor in order to fulfill a commandment”. And it cannot be categorized as “something that’s going to be irretrievably lost” either. Only loss or destruction of something that already exists can be considered “something that’s going to be irretrievably lost”.