"Select all fixtures on truss" selects all the fixture on an already selected truss. The shortcut (on max) is Shift+CMD+U. Could you please add a shortcut so that at the moment of clicking on the truss or pipe while holding a certain key, the fixtures that are on that pipe or truss get selected right away?

The best option for me would be an autogroup function (so when truss gets moved, the fixtures are moved as well). The second best option would be this feature I requested above.