One time long fade?

why dont you just use an animation to make the fading as long as you want? i think its basically just a black screen getting more and more intransparent. 

I guess you could use the shader toolkit. There is a function called ShaderLightness which adjusts the screens lightness.
https://wiki.visionaire-tracker.net/wiki/ShaderLightness_(CMS)

If you would start really dark and then change to normal brightness you could get a transition as long as you would want.

I don't know how dark the screen will get (because I haven't tried it yet), but it is worth a try.

The next version has an action part for this.

The next version has an action part for this.

sounds great  
will it be a fadein/fadeout AP with timings?

A simple work around
Inside the Character Actions make a "called by other action" and name it as you want for example "goaway".
Inside it, change the type of fade (you can change also the delay time in this way).
In the scene where you parts from the island, before the action "change scene"  insert a "call action" and calls the action "goaway" inserted into the character.
In the arrival scene, which I guess is still the same everytime you arrive, in scene actions add a "at beginning of scene" in which you change the fade back to its original state.

Unfortunately I know nothing about scripting, so the Shader Toolkit might be out (and theres nothing on the page you linked)

Yes
Because the character is in the entire game and you can call this action from any scene. Much faster than redo it every time and if you want change the delay time you must do it only once instead to change it in every scene. But you can do it if you want. Simply change the fade in a "at the end of scene".

I put all actions involving different scenes or checks  in character Actions.
In this way keep track of what you're doing without having to remember where you put some action.  

Okay, cool, thank you!

@Paupasia You don't have to create an action for every scene. It is possible to call an action which you created in scene A in scene B. But you are right, using the character to store the actions might be easier to keep track of.


Regarding shader: I just started looking into the shader toolkit a few weeks ago. I can't code a single line, so I was a bit afraid of the shader :-)  But it is really simple (you don't have to understand the code to use it ;-) ).
Just copy the shader toolkit into the script section and set it as definition script.
Then in the action where you change the scene use the actionpart "execute script". Put the line of script there like: shaderLightness(-1, 0) (-1 means total darkness, 0 is the delay-time, here immediatly)
Then a pause actionpart and after that a second execute script-actionpart to turn the light back on, like: shaderLightness(0, 3000) (0 = normal brightness, delay of 3 seconds)

Edit: The Link didn't catch the _(CMS) at the end of the adress. I don't know why... Just add that manually or search the wiki.

@esmeralda Not for all scenes. I think he speaks only of the scene in which leaves the island to  the next island. Whatever the island.
Now, I do not know how many islands he must manage. But, for example, on 4 islands are only 8 instructions. 
Also your idea is useful and with only 4 instructions, but maybe he want a "fade out fade in" effect or something like this. Well ... really I don't know what effect is searching for