Hiya,

Don’t know if this is too late for you but you can use this expression:

(?<=\().+?(?=\))

taken from this page:
https://creativepro.com/favorite-grep-expressions-you-can-use.php

which will find any text inside parentheses, but not including the parentheses.

In your paragraph style go to the GREP style tab and add a new GREP style. In ‘Apply style’, add a bold character style and in ‘to text’, put the expression above.

Tada!