The README and Help menu summarize some functions of Polished Map that involve clicking while holding the Ctrl/Alt/Shift keys. These functions are rather complicated in the block editor, so they're illustrated here.
Simply left-click to place a single tile.
Hold Ctrl and left-click to place a contiguous 2x2 square.
Hold Ctrl+Shift and left-click to place a contiguous 4x4 square.
Hold Alt and left-click to place a sequential 2+2 line in a 2x2 square.
Hold Alt+Shift and left-click to place a sequential 4+4+4+4 line in a 4x4 square.
Hold Ctrl+Alt and left-click to place a sequential 2-2 line in a 2x2 square, with the rows going backwards.
Hold Ctrl+Alt+Shift and left-click to place a sequential 4-4-4-4 line in a 4x4 square, with the rows going backwards.
Hold Shift and left-click to place two sequential tiles in a 2x2 square, with an alternating checkerboard pattern.