Add the name of the user that re-assigned the tasks in the notification email or display

You could use a 'send email' node in your Process Model to create a custom message in conjunction with using the 'Task Smart Services' plugin - forum.appian.com/.../summary

You would also need to add an additional button ('reassign) to your form for this to work instead of reassigning using the default reassign task option. Hope this helps..

Is there a way to capture the owner name who assigns the task by using the out of box "Reassign" feature? I believe we cannot do that.

Unfortunately, not out of the box, but you could try the suggestion above as it could work for your scenario

Thanks

Is there any api we can use to access the process history?

All the public APIs can be found on forum.appian.com/.../ which may help you

May be you can store the values of the old and new assignee in a table and display it accordingly.

Can we change the task notification email? Can we add the name of the user that reassigned the task in the email?

Raveendra, you cannot configure the Appian default task assignment emails. One option is to disable them completely through the Alert Utilities Plugin, and instead use the Send Email node to send your own custom email