Changing the default values in Form Generator

How can I change the default values in a form generated by the Bootstrap 4 Form Generator. I find that for the majority of forms that I create col-sm-2 is too narrow and I am having to do a search and replace on that and col-sm-10 each time. Typically I am after col-sm-4 and col-sm-8 respectively.

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Is there a quicker, better, more permanent way to make this common change? I have many pages with many forms already in existence, and many more to create.