I would like to open a specific scene in a new tab.
In order to open something in a new tab, it must be a separate web page. So the way I’d suggest to do this is that to open the scene you use a Go to URL action that is set to Open in new window (generally a tab for most users nowadays!).
As for the URL field, there is a method (requiring a little code) that lets you use an anchor/hash on a URL that can jump to the particular scene. So you’d use the .html page with this # tag. See the post here for how to do that part:
It means that there is no simple solution for this? Writing code does not scar me, but it’s not very handy in this context…