Shift - PP61 issue

Hi Sap Experts,

Hope you all doing well,

I have been facing a problem in PP61 T-code,  Time administrators manually change the shift in pp61, when they try to change for a public holiday they couldnt change because there is symbol * appears over there!!

* appears over there since the entry is missing in the table for that shift in T77ED, But is it possible to edit * symbol and to change to some other shift.

What is the standard reaction on shift planning on SAP? * symbol cannot be edited?

Could some one help me out on this?

Thanks in advance

Regards

Sriram