how can to change screentime apple-id?

I would assume that screentime is tied to the icloud apple id signed into the device. So you’d probably need to log out and log into icloud with the other apple id , which would make you lose access to the first apple IDs data. It would also reset the screen time data on the device i assume, but i have not tried this.

If you have forgotten the old apple IDs password there‘s a link to recover it when you go to change the screentime code.

Maybe there‘s another solution if you want to explain why you need to change the apple id used to set up screentime.

Set up parental controls with Family Sharing on iPhone --> Set up parental controls with Family Sharing on iPhone - Apple Support

- "With Family Sharing, the organizer can set up parental controls for children in the Family Sharing group. You can use Screen Time to manage how your children use their Apple devices. You can also turn on Ask to Buy, so children must receive approval for purchases or free downloads."

Have you checked out this article?

If you forgot your Screen Time passcode - Apple Support

If it‘s not helpful, please post back with more details.

I would like to know the same thing. I used the apple-id of the phone owner (a child) when setting up screen time and put in a code they don't know, but now they can just use their ID to change the code. I need to change the apple-id to mine so the child cannot change the code on their own without my credentials.