outerjoin works with timetables. However, what you have shared here is not a timetable. Define your left and right keys to be times and the shared variable, then set the MergeKeys name-value pair to true to combine variables.
A = rand(10,1);
B = rand(10,1);
C = rand(10,1);
D = rand(10,1);
times1 = (datetime(2024,5,1):minutes(1):datetime(2024,5,1)+minutes(9))';
times2 = (datetime(2024,5,1):minutes(2):datetime(2024,5,1)+minutes(18))';
Tt1 = timetable(times1,A,B,C);
Tt2 = timetable(times2,B,D);
T_join = outerjoin(Tt1,Tt2,"LeftKeys",["times1","B"],"RightKeys", ["times2","B"],'MergeKeys',true)
