Еще один для MYSQL8.0:
SET @input:="PAY - addition,FILES (aaaaaaaaaaaaaa/bbbbbbbbbbbs i.e. ssss,ffff – i.e. cccccc),DED (ppppppp, llllll, fffff gggg),LOSS (ddddd, hhhhhh – i.e.),F TO G ( “F” is switching to “G”)";
with recursive cte as (
select
0 i,
@input as text
union all
select
i+1,
CASE WHEN instr(text,'(') >0 AND instr(text,')')>instr(text,'(') THEN REPLACE(text, substring(text,instr(text,'('),instr(text,')')-instr(text,'(')+1), '') ELSE '' END
from cte
where i<10
) select text from cte where text<>'' order by i desc limit 1;
вывод:
+------------------------------------------+
| text |
+------------------------------------------+
| PAY - addition,FILES ,DED ,LOSS ,F TO G |
+------------------------------------------+
1 row in set (0.00 sec)