This is something I've thought of requesting as well. This can work like the "Monitor Overlay Safe Zone". In Blender it is called "Composition Guides" and there are eight types of guides available:

Center - Adds lines dividing the frame in half vertically and horizontally.

Center Diagonal - Adds lines connecting opposite corners.

Thirds - Adds lines dividing the frame in thirds vertically and horizontally.

Golden - Divides the width and height into Golden proportions (About 0.618 of the size from all sides of the frame).

Golden Triangle A - Draws a diagonal line from the lower-left to upper-right corners, then adds perpendicular lines that pass through the top left and bottom right corners.

Golden Triangle B - Same as A, but with the opposite corners.

Harmonious Triangle A - Draws a diagonal line from the lower-left to upper-right corners, then lines from the top left and bottom right corners to 0.618 the lengths of the opposite side.

Harmonious Triangle B - Same as A, but with the opposite corners.

Here is the link for more info: https://docs.blender.org/manual/en/dev/render/blender_render/camera/object_data.html?highlight=composition%20guides#composition-guides

Personally I don't believe that we need all this markers.
I just think that we could update the safe zone area markers to fit the standard format which contains a central cross mark and the mid lines on the border.
Check one example here: http://forum.videohelp.com/images/guides/p1716418/safe.jpg
With this kind of tool I never had any issues or limitations

Hi @massimostella,

Your proposed image for the safe margin markers is cool and could be the default, the crosshair in the middle is very helpful indeed. :)

The markers I suggested are very helpful visual guides when doing compositing of graphics/text/image elements over the videos. IMHO it would be a very helpful tool and rather easy to implement. :)

Hi!
Following our discussions, I made some changes to the monitor "safe zone" overlay and the monitor toolbar. Now, when you move your mouse to the right side of the monitor, the toolbar will automatically appear. It contains a "Change overlay" button that will cycle through the available overlays.
So we can now easily create and add new overlays.

The overlay files are simple qml files located in src/monitor/view/
Currently 2 overlays exist:
https://cgit.kde.org/kdenlive.git/tree/src/monitor/view/OverlayStandard.qml?h=refactoring_timeline
https://cgit.kde.org/kdenlive.git/tree/src/monitor/view/OverlayMinimal.qml?h=refactoring_timeline

For those who can compile Kdenlive, you can simply edit these qml files in soure source folder and recompile Kdenlive. The updated layout will appear on monitor. If you have a new nice overlay, attach it here and I can include it.

Currently we are limited to rectangles, because triangles in qml were only added in Qt 5.10

Below is a screenshot of the updated toolbar with the "Change overlay" option.

Hi!

I added three "safe zone" overlays. All of them are the first three Farid's suggestions:

These overlays appears after "OverlayMinimal".

Did you all like it?

I will try create "Golden Law Overlay" soon.

Note: It's not in the main remote/branch. I will create the pull request now.