Any approach to reassign task from Process Model?

arshbirs0001, please take a look at Reassign Smart Service in the following plugin that can be used for that use case.

https://community.appian.com/b/appmarket/posts/task-management-smart-services

is there proper documentation for the same?

I was unable to find formal documentation for the plugin but you will see that using the smart service is quite self-explanatory as per the screenshot below

I want the particular Task to Save and Exit (I've already made that thing using XOR gate), not with that I want a copy of the task reassign to another user with it..........Like from one node it should go to 2 other nodes

I think for this specific thing you want either an AND gate or an OR gate.

AND either takes one incoming flow and process proceeds along ALL outgoing flows simultaneously, or it waits until ALL incoming flows are received and proceeds with one outgoing flow.

OR gateway accepts one incoming flow and proceeds with as many outgoing flows as conditions are met.  If three out of the four conditions are true, for example, the process proceeds along three out of the four outgoing flows.

I think either could be used in a design that does the next step of what you want.

I think for this specific thing you want either an AND gate or an OR gate.

AND either takes one incoming flow and process proceeds along ALL outgoing flows simultaneously, or it waits until ALL incoming flows are received and proceeds with one outgoing flow.

OR gateway accepts one incoming flow and proceeds with as many outgoing flows as conditions are met.  If three out of the four conditions are true, for example, the process proceeds along three out of the four outgoing flows.

I think either could be used in a design that does the next step of what you want.