You can specific a workflow trigger to transition an issue when all sign off steps have been signed off as done. Go to the workflow editor and for your chosen transition, click to view triggers and add a trigger named All Steps Signed Off Trigger. Any applicable issue which has all steps signed off will be transited automatically.
Only steps that are applicable to an issue are taken into account when determining if all have been signed off. If some steps are not available for an issue (because the step is only available in certain projects or for certain issue types) the trigger will not include that step.