Solution
Writing headers on Spreadsheet files is not natively supported by the LabVIEW function "Write to Spreadsheet File". To do so, you need to open a file reference and write your headers, similar to what can be done for a text file. After closing the file reference, you should then move this reference as a file path to the "Write to Spreadsheet file" function along with the data you want to log in the Spreadsheet file.
The code describing this workaround should look like this, as shown in the following snippet: