The ornamental design for this convertible sofa with multiplepositions, as shown and described.
FIG. 1 is a front perspective view of the convertible sofa being in a sofa position;
FIG. 2 is a front perspective view of the side of the convertible sofa being in a sofa position;
FIG. 3 is a front perspective view of the side of the convertible sofa being in a lounge position;
FIG. 4 is a front perspective view of the side of the convertible sofa being in a splitback position where one side of the seat deck is folded down and the other side of the seat deck remains in the sofa position;
FIG. 5 is a front perspective view of the side of the convertible sofa being in a bed position; and,
FIG. 6 is a rear perspective view of the side of the convertible sofa being in the sofa position.