Within Lacerte, no, there is no good way.  All changes inside any given client ("any time that you are not at the Client List view") needs to be done one at a time.
  (On the Client List view, as you know, you can potentially change several clients' information at once for things like efiling, or F4/status updates.)

.

However: if you first establish an ODBC connection to your data, then "yes" you can use an external program (spreadsheet, database, Javascript, Python programming, whatever you prefer) to make changes individually or wholesale.
  https://proconnect.intuit.com/community/permissions/help/lacerte-software-developer-s-kit/00/102313
  https://developer.intuit.com/app/developer/lacerte-sdk/docs/lacerte-get-started

You would connect to the data directory, open the "DATA1-Client Info" file, and search in either column C1_1 (for the Preparer, whose name appears on the signature line) or column C1_56 (Staff Preparer, the one who did actual work on the return).
  Note that both columns store only the Preparer (from Ctrl+O[ptions] | Preparers tab) NUMBER, not storing by name.



Robert Kirk
LTUGtools