According to the source code, in files like https://github.com/BGHDDevelopment/LuckPermsGUI/blob/9cfee7c7c69c01c106bd4d1d65d5132063821d67/src/main/java/me/AsVaidas/LuckPemsGUI/groups/EditGroup.java
Once the user clicked to modify some meta-information (e.g. prefix/suffix), he can't suddenly cancel it.
Instead, he must type something & apply, and then come back to that GUI and delete what he created.
From what I know LuckPerms gives the option to cancel that so it does not need to be built in.