Up to and including in R48, a Group object’s Insertion Point was always the Insertion Point of the first object that was selected when the Group was created; the Insertion Point of a truss structure was the ‘Mount 1’ point of the second truss piece that was inserted; no Insertion Point appeared in either case, and it was impossible to change this point. While in some cases the location of the Insertion Points for Groups or truss structures is irrelevant, there are many cases in which it is, so it is now visible at all times, and it is also possible to change it at will.
To change the Insertion Point for Groups and truss structures: select one (only one!) Group or truss structure, access the EDIT menu or right-click, and then click Change Insertion Point; finally (unlike when changing the Insertion Point for single objects that you’ve drawn or inserted from the Objects Library) instead of choosing a new Insertion Point from a sub-menu, click anywhere (or type the coordinate and press <enter>) to define the new Insertion Point. Tip: use Snaps to facilitate the selection of the new Insertion Point.