The ornamental design for a midfootsupport, as shown and described.
FIG. 1 is a top, front perspective view of a midfoot support, showing my new design;
FIG. 2 is a top plan view of the midfoot support of FIG. 1;
FIG. 3 is a front, right elevational view of the midfoot support of FIG. 1;
FIG. 4 is a right side elevational view of the midfoot support of FIG. 1;
FIG. 5 is a rear elevational view of the midfoot support of FIG. 1;
FIG. 6 is a left side elevational view of the midfoot support of FIG. 1; and,
FIG. 7 is a bottom plan view of the midfoot support of FIG. 1.
The broken lines shown herein show unclaimed subject matter only and form no part of the claimed design. The bottom surface of the midfoot support forms no part of the claimed design.