The ornamental design for a lightingassemblymountingmember, as shown and described.
FIG. 1 is an isometric view of a lighting assembly mounting member according to the present design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a top view thereof.
The broken lines shown in FIGS. 1-7 illustrate portions of the lighting assembly mounting member which do not form part of the claimed design. The lighting assembly mounting member is shown with symbolic break lines along its length. The appearance of any portion of the lighting assembly mounting member between the break lines form no part of the claimed design.