@Roshinin20,
You can only make "additive" changes to an index. For instance, you can add a field, but you cannot modify the attributes of an existing field.
The reason is that as data gets indexed, the operations that happen on the data and the information that makes it into the index is dependent on the attributes of the field.
My recommendation is that during development, lean on enabling capabilities (such as whether a field is facetable or filterable). That may make your index a bit bigger, but I agree with you that it can be pretty frustrating during development to later realize that you wished you had set an attribute on a field.
Thanks,
-Luis