Based on the online help: https://community.pega.com/sites/default/files/help_v721/procomhelpmain.htm.

WorkBaskets do not seem to be applicale in offline mode, as of 7.2.1.

When creating offline-enabled apps that use flows and subflows, keep in mind the following information:

• The worklist displayed in an offline app must be of the Assign-Worklist type.
• The latitude and longitude coordinates are recorded for assignments performed in offline mode.
• Both the client and the server processing date/time stamp is recorded for each assignment performed in offline mode.
• You can create work with parameters.
• pyWorkParty is not supported while working offline.
• You can open work by handle.
• The confirm harness used is the confirm harness that is set on the pyStartCase flow.
• When building an application on top of another application, you cannot reuse flows from the built-on application in offline cases. To reuse flows from a built-in application, save the flows again into the class of the current application.