you could change the size by linking the dimension from the profile sketch of the member, but I do not think that you change which profile you are using. The only way I can think to do that is to create all the profiles you would need in the part then use the design table to suppress or unsuppress as needed.
You will need to create a table with the structural member dimensions for all sections, then you can use a desing table to drive the section sketch.
The table you can copy and paste from the Steel Manual (if you get it on electronic format).
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