If the practice is actively updating the 'preferred clinician' field within the patient details section. This can be filtered within the patient report.
Simply go to 'Reports' > 'Patient' > 'Patient Report'. See below:
This report will then display a list of all patients registered to the practice. See below example:
We can then further filter this report by selecting the +/- icon. See below:
Simply scroll accross and filter the report to be by the preferred clinician you would like, the status as active and the deleted as no. See below:
Select the magnifying glass and this will then populate the results based on the filters. See below:
You can then communicate with these patients via this report or export this report to excel.