Why can't I do this:

d = [x for x in range(7)] 
a, b, c, d, e, f, g = *d

Where is it possible to unpack? Only between parentheses of a function?

You're using Extended Iterable Unpacking in wrong way.

d = [x for x in range(7)]  
a, b, c, d, e, f, g = d
print(a, b, c, d, e, f, g)

Where it's possible to unpack? Only between parentheses of a function?

No,

* proposes a change to iterable unpacking syntax, allowing to specify a "catch-all" name which will be assigned a list of all items not assigned to a "regular" name.

You can try something like this:

a, *params = d
print(params)

Output

[1, 2, 3, 4, 5, 6]

Usually * (Extended Iterable Unpacking) operator is used when you need to pass parameters to a function.

Note

Javascript equivalent of Extended Iterable Unpacking operator is called spread syntax.

d = [...Array(7).keys()]
console.log(d)
var [a, ...b] = d
console.log(a,b)