Currently, a job can be downloaded as a bilingual MXLIFF, TM, or DOXC file, but it is not possible to download it as a bilingual XLSX file which is a format required by some online spellchecking tools.
Available workaround (if any):
Download a bilingual DOCX and manually copy-paste the content into a XLSX file, some further editing is necessary.
It is possible to download a job as a bilingual XLSX.
A bilingual XLSX file format is more suitable for some online spellchecking tools.