Complex sentence: The left panel shows a swooning Virgin Mary supported by Saint John the Evangelist, both dressed in pale folded robes, and again presented before a draped red cloth (that shows the creases of having been recently unfolded).
Split into simpler sentences: The left panel shows a swooning Virgin Mary supported by Saint John the Evangelist. Both are dressed in pale folded robes, and again presented before a draped red cloth (which given the creases appears to have been recently unfolded).