Since we want to assign these four unassignable missions, we would like to increase resource availability around the time they should fly. To do that, we select them all and create a resource view to inspect the contention of the alternative resources that could be used by these missions.
Th green band in the capacity window show the interval the missions should fly. We select the four alternative resource by dragging the mouse around the region we want to select (red box) and use the menu command Schedule | Automatic Merging to ask the system to automatically compute all possible mission combinations in that interval.
After the system has executed its task, we go back to the combined mission sheet and notice that only one new mission combination was created. The other was the result of merging the retrograde mission.
Maybe the automatic combination has opened some resource capacity that can be used by the currently unassignable missions. Going back to the unsassignable sheet, we select them all and ask the system to feasible allocate the missions. As we can see the merging opened space for allocating two of the missions.