Creating a permission set that grants Edit access to leads and assigning it to the marketing managers is the best way to grant them the access they need, without affecting the other users on the marketing team profile.

Explanation
The account relationship is a standard lookup field on an opportunity. A lookup field allows the user to select a record from another object and link it to the current record. The account field on an opportunity allows the user to select an account that the opportunity is related to. The stage relationship is not a lookup field, but a picklist field that indicates the sales stage of the opportunity, such as Prospecting, Negotiation, or Closed Won.
The quote relationship is not a standard lookup field, but a custom lookup field that can be created to link an opportunity to a quote. A quote is a record that shows proposed prices for products and services.

The Object Manager is where the associate should go to see the information about all the objects within their company's instance and identify which are custom objects. The Object Manager allows the user to view and manage the metadata of standard and custom objects in Salesforce, such as fields, page layouts, record types, buttons, and actions. The Object Manager can be accessed by clicking the Setup icon in the header, then clicking Object Manager. The custom objects are indicated by a blue icon with a white asterisk, while the standard objects are indicated by a gray icon with a white letter. The App Launcher is where the user can access all the apps and objects in Salesforce, such as Sales, Service, Marketing, and so on. The App Launcher does not show the information about the objects, such as fields, page layouts, or record types. The Global Search is where the user can search for records across multiple objects and fields using keywords or phrases.
The Global Search does not show the information about the objects, but only the records that match the search criteria.