For Lead Gen Form campaigns, conversion actions can be added to a campaign via:

For LinkedIn Lead Gen Form campaigns, you have two primary methods to associate conversion actions. The most straightforward way is to edit the campaign details directly within the campaign settings. This allows you to select and apply existing conversion actions or create new ones specific to that campaign. Alternatively, when you are in the process of creating a new conversion action, LinkedIn provides an option to associate it with an existing campaign by entering the campaign's name. This flexibility ensures that you can accurately track conversions for your Lead Gen Form campaigns, whether you're configuring an existing campaign or setting up a new conversion event. The option "Only via ‘Edit campaign details’" is incorrect because it overlooks the ability to link during conversion action creation. "By adding the campaign name when creating the conversion action" is incomplete as it misses the campaign editing method.