I came from mainframe world as well.

I gave you 3 samples of scripts.

The first CREATE's a table. You said you have new tables.

The second modifies an existing table adding a field in the middle of all the other fields and keeping the data intact.

The third shows the creation of a function - if you do not use STORED PROCEDURES or SCALAR functions in your DB then ignore that.

Point is that I do not use SSMS to modify table structure.

All SSMS does is create a script internally to modify an existing table - usually coping off the entire table to a temp location and dropping/re-creating that table with new columns and then re-loading it from the temp table.

If you look at my second example I am using a combination of FIELD RENAME and FIELD ADDING techniques to add a new field - shifting an existing field to the right and then re-loading just that one column.