filecontent = fileread('YourFile.txt');
content_by_line = regexp(filecontent, '\r?\n', 'split');
content_by_field = regexp( content_by_line(:), '\t', 'split');
max_fields = max( cellfun(@length, content_by_field) );
cellpad = repmat({{}}, 1, max_fields);
first_n_fields = @(C, n) C(1:n);
padded_content = cellfun(@(C) first_n_fields([C,cellpad], max_fields), content_by_field, 'Uniform', 0);
desired_output = vertcat(padded_content{:});
This reads the file and splits it into lines and then splits the lines into fields. Then it finds the line with the most fields, and constructs padding as long as that. It then goes through and pads each line and takes the first N outputs: in this way without having to test how many fields there were on the line, each line is padded out to the same length. Once you have the cell array of cell arrays that are all the same length, a simple change converts it to a 2D cell array.
