The ornamental design for a trailerhitchsupport apparatus, as shown and described.
FIG. 1 is a right side elevational view of a trailer hitch support apparatus showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational thereof;
FIG. 5 is a left side elevational view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken line showing of portions of the trailer hitch support apparatus is included for the purpose of illustrating environment and forms no part of the claimed design.