I understand that you want to include the missing timestamps using [] in your newtable. You can make use of the 'intersect' function to compare the durations in the complete time array with the durations in your table. You can use the below example for your reference:
%%Initalization
% This creates the Time and values array
times = duration(0, 1, 0:20)';
vals = rand(21,1);
Perform intersection with the new duration variable
newtimes = duration(0, 0, 0:120)';
result = cell(length(newtimes),1);
%get the duration, the duration's index in times and the duration's index
%in newtimes
[dur, itimes, inewtimes ] = intersect(times,newtimes);
v=num2cell(vals(itimes));
[result{inewtimes}] = deal(v{:});
newtable = table(newtimes, result);
In the above example the first section initializes the times and vals similar to your 'mytable'. The second section creates an array of newtimes which contains more duration values than the first times variable. You then find the intersection and its indices between the two time variables and then assign the values to the corresponding indices in the newtimes variable. With the indices available, you would just have to do a cell array assignment as shown above.
You can refer the following link for more information on the 'intersection' function:
Hope this helps.
