Why do the parentheses disappear in the rule

The setup editor will automatically remove parentheses that are not logically necessary.

The GSE will only display parentheses in a rule block if they are logically required, and will remove them if they are not. For example the following would keep the parentheses

if value > (1 + 2) * (3 + 4) then

severity ok  endif

The following would not

if value > (1 * 2) + (3 * 4) then

severity ok  endif

this formats to:

if value > 1 * 2 + 3 * 4 then

severity ok  endif