I’m trying to open a document with “hide whitespace” enabled, but every time I close and open the document, the option is disabled again. Is there any way to save view preferences?
Modify the template used to create your document (or create a special “Hide white spaces” custom template).
This won’t change existing documents, but new ones should be as you wish.
For advice on creating a template see https://help.libreoffice.org/Writer/Creating_a_Document_Template . Or consult chapter 10 of the Writer 6.0 user manual. You can download the manual as a PDF, free of charge, from the LO website’s documentation page, English documentation | LibreOffice Documentation - Your documentation for LibreOffice .
Addendum for koechophe’s comment
Not that I can advise on.
You might consider the template changer extension at https://extensions.libreoffice.org/extensions/template-changer and look at past discussions on changing the template for existing documents, for example at How to change template of the document (LO 4.1) and the OpenOffice forum Change The Styles Template for Existing Document (View topic) • Apache OpenOffice Community Forum. These suggest it is possible, but with difficulty.
Of maybe somebody here can offer better help.
Is there no way to do this for existing documents?