In the editor, the spell check will dynamically flag spelling errors by underlining them in red. This is the default behaviour in a job.

If, however, you want to change this and require that the user must manually enable this feature in every job, simply uncheck this box.

'Check while typing' can be enabled/disabled in the Job Editor in the 'Spelling' panel, as shown.

NOTE:
The word 'gears' is marked as a spelling error here, because the target language of this translation job is German.