Re: Change customer specific fields (KUT) afterwards to read only

you can also check via adapt mode and edit this screen with new tab.

Under the screen Layout you can see Tab,

select that tab and then You can check all the tab, there would be chance "Field and Action" tab is not checked for you.

Enhance the Business Role screen via Adaptation mode and add this "Field and Action" tab.

HTH

Thanks

Sunil