If your developers want to use SAP Web IDE, use identity provider users for them to ease log on to the Neo enviroment.
If you have followed the steps for setting up a custom identity provider, you have already created a developer group in the tenant for the Identity Authentication service (see also Setup of a Custom Identity Service). Now you need to create a developer group in the Neo enviroment and map this group to the developer group in the tenant for the Identity Authentication service.