Hi,
How I would do this using V6.x
Example:
First add a variable to the skin:

- 01_add_variable.png (23.58 KiB) Viewed 1403 times
Then add a rectangle and adjust it's position and size:

- 02_add_rectangle.png (33.27 KiB) Viewed 1403 times
Then using the rectangles background colour picker change it to black with some alpha to make it translucent:

- 03_cahange_colour _alpha.png (99.17 KiB) Viewed 1403 times
Deselect visible then under the visible logic block add the following:

- 04_logic_block.png (59.83 KiB) Viewed 1403 times
Make sure any element that should be in front of the screen tint when it shows is above it in the skins tree.
To show the screen tint using a button or hotspot will need the action:

- 05_show.png (63.12 KiB) Viewed 1403 times
And to hide:

- 06_hide.png (53.18 KiB) Viewed 1403 times
You can even give the screen tint the hide action so it hides on click.
Regards,
Hopki