The Dropbox Add-On provides hooks that can be used to modify the default functionality or extend it. For more information, review the Dropbox category.
Looking for information about what properties the Dropbox Upload field uses in the Field Object or what format it』s value is stored in the Entry Object and how you can access it? Then take a look at the GF_Field_Dropbox article.
Because the Dropbox Add-On is built using the Add-On Framework, it also inherits any hooks available in the framework methods it uses such as:
gform_short_slug_field_value for changing the Dropbox Upload field value before it is used to upload the files to Dropbox.
gform_short_slug_error for performing a custom action when the add-on experiences an error processing a feed.