Use map to workflow variable, it may solve your problem 

just change "map to Performer's HOD" to "map to workflow variable"

here the example link Map to Workflow Variable

Hope this help 

i still not get it right. if i set 'assignee' as a workflow variable in transition from Activity 'Fill Claim Form' to Activity 'Manager Approval Form'. What expression i should type as 'assignee' value? e.g status=='Approved' , status=='Rejected' thankyou :)

Sorry i'm not good with explanation so let me show you this example.

First set workflow variable (if you set it on workflow designer it may warn you this "warning status unused variable"  just do not worry about it because we use it to store manager's name. ) 

Second, in manager's name field (field that you want to type your manager's name) set workflow variable to match with the name that mention at the first picture.

Finally, map to workflow variable like this picture below.

then it will send Performer's form to the next participant who has his username match with the manager name field at step 2.

This method may not directly solve your problem but it might give you another idea.

Yeay, its work! thank you so much, worrarat.. at first i give variable name in transition between Activity.. But, in the fact the variable just need to be added in properties of the process. :) bless you!