The Marksman
Virgin
The eye icon sets the variable to visible.
The two squares icon doesn't change the currently set visibility of the variable.
That means that you can make a variable visible in one branch but keep it hidden in another branch.
If the branches merge, the No Change icon keeps the visibility status of the variable, so the reader who chose the first branch still sees the variable while the reader who chose the second branch still doesn't see it.
If the two squares icon is used the first time a variable is introduced, it works the same way as the eye icon.
(This is also described in Conditional Branches 6. Visibility.)
Gracias.