All workflows can be modified and saved.
If the submit button does not appear at the top of the workflow, there is a possibility that the workflow has either not been completed or the workflow has pre-requisite workflows which have not been approved.
To find out what the pre-requisites are for the workflows:
Navigate to Administration -> Idea Definitions.
Select the applicable Idea Definition
Select workflows on the top right
Select an applicable workflow
Navigate to the "Pre-Requisites" tab.
This will now show you all workflows that need to be approved prior to the selected workflow being allowed to be submitted for approval.