We have recently changed the HideWhiteSpace menu item to ShowWhitespace by enabling the later by default. Refer bug 124686 This changes are not reflected in notebookbar UI. Opening a ticket to port these changes to notebookbar UI as well.
Based on Shameem's comment, changed the status to NEW for Bugzilla cleanup purpose. Bug 124686 is marked as RESOLVED FIXED. This bug adds notebook bar UI changes in addition to what was done in previous bug fix.
andreas kainz committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/core/commit/7ac7fb03e4fe3a3a7996631e725deea6e3edc85c tdf#131746 HideWhitespace is now ShowWhitespace It will be available in 7.0.0. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.