When I open a libre document I want to automatically insert todays date and be able to start writing at the top of the document. Like a daily diary or journal.
This is possible with a template. Design your template as you would an ordinary document. Record in it all your custom styles.
In addition, enter the default initial content. Today date is set with Insert>Field>Date which inserts the “fixed” variant of date, i.e. it retrieves its value when the document is created and never changes afterwards when you reopen it.
Use File>Templates>Save as Template instead of the usual Save command.
To create a new document, File>New>Templates and select your user template. This will create a new document with the initial content defined by the template. The fields will be computed and you get the date of document creation.
For more details about templates and fields, read the Writer Guide.
To show the community your question has been answered, click the ✓ next to the correct answer, and “upvote” by clicking on the ^ arrow of any helpful answers. These are the mechanisms for communicating the quality of the Q&A on this site. Thanks!
In case you need clarification, edit your question (not an answer which is reserved for solutions) or comment the relevant answer.
Thank you.