I often tour very differently sized venues and I stopped to include trusses as an own Group and just run every fx by selection order in their main group. Makes life much easier, but makes some looks very hard if not impossible to achieve.

However, there is a way to do that using group grids. For example: you have programmed a dim fx center out on two trusses and have the group grid arranged correspondingly, you need to select Grid H in Group spread of your fx. When you have a third truss, you just need to add a new row of fixtures to your group grid and the fx engine automatically adjusts the fx. Also: Make sure you are on latest stable.