If you want to share your task with someone else use the little arrow at the top right.
Choose if the invited user will View, Edit or Perform the task or if you want to Assign the task and upcoming tasks to a new performer.
Note: The share function can be disable completely or partially via the participant configuration for a specific role.
In that case only an administrator can share the task.
If you choose to share the task with View as user right, the invited user can only view the task he or she may not edit or complete the task as this is restricted. By sharing a task with the user right to edit the invited user will only able to edit the information in the form and save changes, he or she will not able to complete the task.
If you indent to share a single task with the user right to perform it, enabling the invited user both edit and complete the task share as perform is the right option.
The perform option can be assigned to any user or groups within the space.
As stated above if your intention is to share the task and all upcoming tasks for a specific role, Assign task would be the best option. Remember that if you choose to share as Assign task the user sharing the task will lose his or her user right to perform the task, if the user name is not included in the field of users and groups the task is shared with.
The assign option can only be used for user that is already assigned the role. It is also possible to disable the assign function for a specific role.
NOTE: Worth mentioning regarding restrictions of the share as functionality in correlation with a role mapped lane. Is that if there are an active role map at the specific lane you may choose to share as; View, Edit or Perform with all users in the space. However, if you intend to share as Assign task in order to transfer the user rights to perform the current task and upcoming tasks this will not be possible, as no additional user names will appear. Except the specific role mapped users that will be available and displayed. If the intention is to share as Assign task in correlation with a rolemapper the role mapped field must be changed, possibly by a space admin. It will then be possible to use the Assign task utility to transfer the user right for the current task and upcoming tasks successfully.