Hi I use Oracle SQL developer to develop PSQL .sql files I managed to connect these files with subversion, If I go on the History tab:

I can see the diff

Is there a setting in SQL Developer that I can see a quick diff in the Worksheet without looking in the History tab

Two things.
if you're using our subversion extension, use team > subversion > pending changes. Then you can see the differences specifically in the subversion panels w/o having to mess with the history tab in the SQL Worksheet.
or, in the sql worksheet, SPLIT the editor - right-click on the editor tab