I am trying to make the class "NamespacedHolderWrapper" public with an access transformer. I have specified it in "build.gradle" at the correct position but a gradle reload does not apply the changed in Intellij Idea.

Please show the build.gradle and the accesstransformer.

when you change the build.gradle, a small hard-to-notice floating window shows up in intellij idea - above editor, close to the right side.

try increasing the version in build.gradle if that's where you keep it. then click the button with two arrows forming a circle and grab an apple. in about 5 minutes, your access transformer lines will be applied (assuming you uncommented the AT line in build.gradle).

It works for all other transforms. Just not making classes public