Questions: Education & Career

NOTE: THIS SAME COMPANY JUST ANOTHER DEPARTMENT

I am now working in a customer service under Airline account. It is my first time to work in a customer service job because my experience was purely back office like finance and operations. I am struggling to this job and even the supervisor know about it for sure.

I applied to another department that is back office operation under the same project Airline (but purely back office not customer service) and passed the excel exam and got final interviewed. I told them that my supervisor didn't know about my application because I am not yet sure if I will be hired. And, they said the hr will just inform me if I am hired and will advice the next step for me and do proper communication.

My question is, should I tell my supervisor that I was interviewed by other department in back office position now OR should I wait until there is already announcement that I am hired before I tell the supervisor?

I am so confused if I tell now, he might support me to my transfer, If I tell now, he might dislike me and do some troubles for me especially if I am not hited.

If I tell later after I am hired, he might be so mad at me or think I disrespect him.

(NEED ADVISE FROM PEOPLE)