Zmóžńće JavaScript we wobhladowaku, zo byšće strony pomocy za LibreOfficeDev pokazał.

Table Boundaries

Shows or hides the borders of table cells that have no set borders. The boundaries are only visible on screen and are not printed.

Přistup k tutomu přikazej …

Z menijoweje lajsty:

Choose View - Table Boundaries.

Z powjercha z rajtarkami:

On the View menu of the View tab, choose Table Boundaries.