This Bugzilla instance is a read-only archive of historic NetBeans bug reports. To report a bug in NetBeans please follow the project's instructions for reporting issues.
There should be an option to remove git stashes, or clear them out "git stash clear". You can create stashes, but can't remove them. Maybe even an option to remove the stash item after you've applied it successfully?
Team -> Git -> Repository -> Repository Browser... Expand Stashes, select a stash you want to remove and either press Del or select Drop Stash from the popup menu?