if you don't want a variable you can use this block to not create a new variable
is the variable you actually want too cumbersome to grab? perhaps it's local to another sprite (and you're using the tell block), or it's too far up in the script, or it's global but you don't want to switch palette. this block can go right into the script where you want it and won't make a new variable.
Clever.
"Dangling" 
does the same..,
coming back here because i realized the use cases i came up with last minute makes this sound like a legitimate block.
don't use this. it's a joke, it'll probably break horribly in some number of updates.
script variables makes a variable, this block doesn't. you can put this block in the script and it won't make or override the variable.
But why?
You can put the "script variable" block anywhere in the scripting area outside of the script.
Of course, whatever floats your boat...
That's a really smart idea! I constantly do projects with clones interacting with one another, and sometimes a clone will need to access a "for this sprite only" variable, or a script variable, that it doesn't actually have. I'll probably try to implement this in future projects.
I actually no joke used this on a project today. Thanks!