As is typical, I found a solution to my own question.
This syntax will allow you to bring over the missing times from the right table.
Tleft = timetable(seconds([1;2;4;6]),[1 2 3 11]');
Tright = timetable(seconds([2;4;6;7]),[1 3 6 7]');
[T1,~,iright] = outerjoin(Tleft,Tright,'Keys',{'Var1','Var1'});
T1.Time(isnan(T1.Time))=Tright.Time(iright(isnan(T1.Time)))
T1 =
6×2 timetable
Time Var1_Tleft Var1_Tright
_____ __________ ___________
1 sec 1 1
2 sec 2 NaN
4 sec 3 3
6 sec NaN 6
7 sec NaN 7
6 sec 11 NaN
I hope this help someone else.
Outerjoin need a MergeTime function similar to how it has MergeKeys.