You can use the following shortcut keys in charts.
You can also use the general shortcut keys for LibreOffice.
Shortcuts in Charts
Select next object.
Select previous object.
Select first object.
Select last object.
Move the object in the direction of the arrow.
up/down/left/right arrow in pie charts
Moves the selected pie segment in the direction of the arrow.
F2 in titles
Enter text input mode.
Open group so that you can edit the individual components (in legend and data series).
Exit group (in legend and data series).
Reduce or enlarge the chart
+/- in pie charts
Moves the selected pie segment off or into the pie chart.