How can I update party names in a clause without manually overwriting?

If you wish to adjust the terminology before inserting a clause in the document, you can do so by clicking on the wrench icon :

Next, a new menu appears where you have the option at the bottom to replace a term in the clause with a custom term chosen from the open document (or by entering a term in the field next to the term):

After choosing the term, you simply click on ‘Redraft’, and the clause terminology will be adjusted with the terms chosen by you:

The clause with the adjusted terms can then be inserted into the document using the plus icon.