I searched without results so I'm asking for the best/right way to do this: I need to add to add_action row snippet in a plugin init function. There's no hook or filter available so I'm unsure if the right way to do this is to make another plugin, checking the dependencies of the other two plugins (The snippet that I need to insert integrates the functionality of one addon in the other plugin) and extend the class of the that plugin.. Any hint? Because editing directly the plugin file works but that's not really the best solution...

Thanks everyone, hope I was understandable.

I add some details: with the Gravity Form Partial Entries addon, the plugin that send the data to Infusionsoft are not working as it should, so I need to add the hooks 'gform_partialentries_post_entry_saved' and 'gform_partialentries_post_entry_updated' to send data also when the form are not submitted. But the code depends on the Infusionsoft plugin.