Paste clipboard content (including native tables or tables copied from Calc or other spreadsheets) as nested tables in empty cells and at cell starting cursor position.
Choose Edit - Paste Special - Paste Nested Table.
Right-click on the target table cell to open the context menu and choose Paste Special - Nested Table.
Pasting table data in Writer tables overwrites the contents of the existing cells, when the cursor is in an empty cell or at the beginning of the first paragraph of a table cell.