Formatting can be set for merge fields whose data type is Date or Date/Time. The formatting is set by separating the field name with a comma. Available in Ver. 2.0 or later.
e.g. {!Case.TestDate__c, MMM. d, yyyy}
Result: Mar. 1, 2024
*In Excel, merge fields cannot be formatted. Set the format from "Format Cells".
Instruction manual
Formatting of Date and Date/Time Fields