Regarding the 1st question, the solution will be like the following. The same method can be applied to solve the 2nd question.
% Original table
SM_A1_X11 = [5;1];
SM_A1_X03 = [10;30];
SM_B1_X10 = [2.5;20];
SM_B1_X07 = [5;0.23];
T = table(SM_A1_X11, SM_A1_X03, SM_B1_X10, SM_B1_X07);
% Extract variable names
varNames = T.Properties.VariableNames;
% Sort by 'X??'
varKey = regexprep(varNames,'SM_[\w]1_','');
[~, idx] = sort(varKey);
% Sorted table
T = T(:,idx);
