From The Document Foundation Wiki
    < Faq‎ | Writer

    How to repeat a table header line on all the pages of a document where the table appears

    This is the default option in LibreOffice when you create a new table. If you are working on an existing table or if you use a template, follow these steps:

    1. place the cursor anywhere in the table;
    2. right-click to display the contextual menu and select Table Properties... ▸ Text Flow [tab];
    3. Under the Text Flow tab, check ☑ Repeat heading;
    4. set the number of lines you want to repeat; and
    5. click OK.

    To modify the default option:

    1. Tools ▸ Options ▸ LibreOffice Writer ▸ Table;
    2. under New Table Defaults select (un)check Heading and Repeat on each page; and
    3. click OK.