[GENERAL] Using Variables in Queries

Hello,

In other database servers, which I'm finally dropping in favor of Postgres, I can do the following (mind you that this is for illustration only, I do not actually write queries like that):

DECLARE @query varchar(64) = 'red widget';

SELECT *
FROM products
WHERE col1 LIKE @query
   OR col2 LIKE @query
   OR col3 LIKE @query
   OR col4 LIKE @query
   OR col5 LIKE @query

The point is, though, that I can change the @query variable in one place which is very convenient.

Is it still true (the posts I see on this subject are quite old) that I can not do so in Postgres outside of a stored procedure/function?  And if so, what's the reason of not adding this feature?  Seems very useful to me.

Thanks,