Greetings
This is a 1366 x 768 panel so everything gets scaled one way or another. On the 1080p sets there is a control called HD Size ... 1 or 2 ... and 2 does dot by dot (no overscan).
No dot by dot is possible on your set since nothing is 1366 x 768 in the HD realm.
In this generation of display, there are no overscan controls in the immediate service menu. In the engineer menu ... likely ... but no one outside panasonic has access to that area. Even repairmen do not get access because they have no business being there.
The only way you might get no overscan is to feed it a 1366x768 signal ... but the manual says it won't accept that signal.
regards