I have a project to create vendor on boarding/lead nurturing program. I am looking at the native NS vendor dashboard currently. Does anyone have any suggestions for allowing vendors log in, fill out registration forms and upload files outside of netsuite? The main challenge is to allow vendors to fill out piece by piece the requirements we need to certify them as an approved vendor. The vendor will need to be able to partially complete and save the information to come back later and finish or add to their registration.

You can use the vendor center to give access to the vendors. Create their account then give them vendor center access, use a custom field or workflow to assign a status such as activation completed or so (best to use both in combination). Create a web form for your registration and link it to vendor center - where vendor can complete their registration, once form completed workflow will trigger and complete the activation process. This is just a process flow suggestion.