How do you create universal standard styles and formats that are present in every document?

I have many documents that I maintain which have been written over the past several years. Some were created in MS word and imported to LibreOffice, but most have been created in Libreoffice Writer. One of the things I must do when editing or updating them is to apply a standardized approach to formatting, i.e. a certain font and font size for heading 1, 2, 3, etc. Some docs have code snippets in bordered boxes, and I have created a custom style for that. My problem is that it seems that the styles and formatting functions are unique to each document. If I make a custom formatting style like “Code Snippet” I want to be able to access it in any document, without creating that same custom formatting style in each doc. Same goes with standardized headings. When I change Heading 1 to be 18 point Liberation Serif in bold, I want to be able to open any other doc, highlight some text, and make it Heading 1 and have it change to 18 point Liberation Serif font in bold, not something totally different. There has to be a way to do this!!! I know it’s probably something I’m not doing correctly. Can anyone help?

Create and save a new default template.

See [Tutorial] Creating a new default template (View topic) • Apache OpenOffice Community Forum for instructions.

The default template is automatically applied to new documents only. Any document has its set of styles, written to the document itself, that makes its styles separate from any other document. Also, this makes the document stand-alone, able to be sent over the net to another person who doesn’t have your templates, and be opened there correctly.

However, LO has options to make your life a bit easier. You may import styles from another document using StylesLoad Styles... menu (Styles and Formatting sidebar also has relevant button). In the Load Styles dialog, you may select those style categories you need, and also make sure than you select Overwrite option that allows to replace already existing styles with those that are in the source file. Then you select your saved template, and have these styles in your open document.

Also, using master documents, the style settings for child documents are defined in master document… but that’s probably not your case.

@icb As you maintain existing documents, it is too late to base them on a custom template. However, the custom template is the right file to store the common styles and you can load the styles from there (see @mikekaganski’s answer)?