From The Document Foundation Wiki
How to deselect one sheet in a spreadsheet after having selected several
Choose one of these two methods:
- Use the same operation as when you selected them: CTRL + click on the tabs of the sheets to be deselected. This can prove tiresome if there are a significant number of sheets.
- Faster: ⇧ Shift + click on the tab of an active sheet. All the other active sheets are deselected.