Letters in braces

Hello, I’ve gone through the existing bracket topics but either I’m an idiot or it doesn’t work the way it should (I opt for the first one here). I need to search all instances:
Source: (A)
Target: Lack od A
The same applies for other letters. Without power search it ignores brackets. When I use “(A)” for source and -@1 for target, with power search, it doesn’t work. What am I doing wrong? Please, help.

You must use the expression "(A)=1" in source. It assigns to variable 1 the resolved value of the expression in the currently parsed segment. The resolved value can be recalled with the expression @1. The search should be the following:

Source: "(A)=1"
Target: -@1
Search mode: Regular Expressions
PowerSearch: On.
Match Whole Word: On.
Case-Sensitive: On (to find only uppercase A).

To search other letters in the same search such as B, C and D, the source would be "([ABCD])=1".

Thank you so much! It works perfectly.