On Windows, the official separator character is a backslash. Least Windows users or administrators actually know that on other OS it is a forward slash. So when typing in a JVM Option that has a path value, they will type in a backslash.
But when restarting the domain, the backslash is gone. The GUI shows the path without any backslashes.
This is a blocker as nobody could gess how to fix it, so if the option is essential for the particular use case, GlassFish cannot be configured to run.
As Windows people do not know that a forward slash will do, this is a blocker for those people. The GUI not even tells that the backslash is not accepted or that it should be replaced by a forward slash. Typical *ix-developer agnostic way to think about the world: "There is no Windows, and even if there would be something like that, it would not have any impact on me." Well, it HAS impact.