For a frame trussed from below, compression members are to be modelled perpendicular to the inclined beam. The member length and the intersection with the horizontal beam are defined.
One way to do this would be to rotate the grid 90 degrees and place the origin in the respective node. Then you can place the compression members along the grid points.
Another possibility is modeling with a polar coordinate system. However, this requires precise angle information.
Thus, the solution with the least modeling effort is to use the alternative input modes of members.