To edit a chart title that you have inserted into a LibreOffice document:
Double-click on the chart.
A gray border appears around the chart and the menu bar now contains commands for editing the objects in the chart.
Double-click on the default title text. A gray border appears around the text and you can now make changes. Press Enter to create a new line.
If no title text exists, choose Insert - Titles to enter the text in a dialog.
A single-click on the title allows you to move it with the mouse.
If you want to change the formatting of the main title, choose \<emph\>Format - Title - Main Title\</emph\>. This opens the \<emph\>Title\</emph\> dialog.
Select one of the available tabs in the dialog to make modifications.
Click \<emph\>OK\</emph\>. In your document, click outside the chart to exit chart editing mode.