Why aren't I getting all 4 rows in my table?
Matlab does exactly what you asked. As you've shown E is a 4 (rows) x 1 (column) cell array. E{1, :} is the content of the 1st row and all the columns. There's only one column, so E{1, :} is the same as E{1, 1} or E{1}. The content of E{1} is a 1 (row) x 4 (column) cell array, hence you only get one row out of cell2table.
Note that if E had more than one column, then cell2table(E{1, :}, ...)| would have been equivalent to:
cell2table(E{1, 1}, E{1, 2}, E{1, 3}, ... )
which would have most likely errored unless E{1, 2}, etc. contained valid options for cell2table.
To convert your cell array of cell arrays to a table. First concatenate all the rows so you have a 4x4 cell array, then call cell2table:
T = cell2table(vertcat(E{:}), 'VariableNames',{'IO_Type', 'Name', 'Type', 'Range'});
You may want to review how you construct E so it is a 4x4 cell array (of char arrays) instead of a 4x1 cell array of 1x4 cell arrays (of char arrays)
