Where to find source code for Actions menu

Hello Community,
I want to add an item (e.g Change Status) in Action Drop-Down button. In which directory i will find the source code(.js & .py files) of action drop-down button

I can’t say exactly where the Action button code lives. But to search the code this may help Reapply customization on Duplicate - #4 by clarkej

It lives here:


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