Not really sure what you are talking about. If you have five companions (won't happen until level 40+) you can send all those companions out doing missions in the same crew skill. But as soon as they are done, the mission list repopulates. The only missions that are not this way are the "discovered" missions that come from critting while running slicing missions. These are a one shot, but even then you can get the same mission from a different mission discovery item.
Thanks that is what i was looking for that the list repopulates sorry if i didn't come across the right way but you figured it out just fine