Using the “arbitrary text” feature, then insert dynamic expression and lastly, converting the arbitrary text to a number worked.
However I am dissatisfied with this solution as it will get very messy with increasing number of nested brackets. I do not know why they had to remove the beta expression writer…
The parenthesis continue to exist. You need to go in settings > versions and experimental features to activate them. This should be like what you get with the Beta. The main difference are not on the expression itself, but how you can modify it (adding something in the middle of the expression is not possible anymore)