Can it? Maybe. But there would certainly be some limitations or possible issues. The best way is to certainly use the built-in "Selectively Paste Event Attributes" option and, possibly, request some modifications to that screen. For example, maybe an option could be added that allowed you to check what you want checked/unchecked by default and that setting could be saved for future uses of that option.

In my testing, it appears to be remembering what I've checked/unchecked on both the main screen and secondary option screen between usages.

@jetdv That request I made to the vegas team, I thought there was no way to do it through a script, that's why I didn't even ask you. But this I had hopes of being possible. And after seeing that you managed to do the other one, I thought it was possible to follow the same logic.

About the current state of this role. The following is. When we copy once and paste and uncheck the option. When we paste again, the option remains unchecked. But when we are going to copy again the option is checked again. And yes, I wish there was an option in the vegas preferences so we could always choose checked or unchecked.
But another reason I want a script for this is to define a keyboard shortcut. All scripts I define a shortcut key to trigger it. I understand why he unchecks it, it's because now the user may want to make another type of collage, but in my case I wanted to define always the same collage mode.

@lan-mLMC Interesting. Did not know. But I didn't like not being able to copy the fx with CTRL + C, having to define another shortcut for the "copier" of the extension. But it works. @jetdv I still preferred something with no interface and no pop-up message every time I run it. If you're still interested in doing that, that's fine. But I really don't need it anymore. Thank you for your attention.
 

Products with UI are generally thought to be better, of more freedom degree, and can satisfy the needs of more people than just one or two.

The script wouldn't be able to access the "CTRL-C" information. For this to work, it would have to be a custom command, you would need to select the source and then tell the Custom Command "this is the source". Then you would have to pick the destination events, tell the Custom Command what you wanted copied, and then tell it to copy it. The existing method is much better for this so, perhaps, the dialog can be tweaked to allow saving of the default settings. But that will be up to Magix.