Which of the following tasks can be performed in the Sophos Partner Portal?

Registering a deal in the Sophos Partner Portal is indeed a key task that partners can perform. This functionality allows partners to formally acknowledge potential sales opportunities and seek protection for those deals, which can be beneficial in avoiding channel conflicts. By registering a deal, partners can communicate their efforts to Sophos, which can lead to better support and potentially incentives associated with the sale.

In the context of the other options, while they may represent important activities available within the portal, they do not encompass the specific mechanics of deal registration. Accessing marketing tools and resources or managing leads are essential for partner operations but serve different purposes within the operational framework of a partnership with Sophos. Similarly, training and certification access helps enhance knowledge and skills, but it is not a task that directly involves financial transactions or sales opportunity management like deal registration does.