Physical information are ease to transfer to TDM, you need only do RE from DB or from SQL Create Script. Next step are logical information as model layout, captions, descriptions and others. I’m not familiar with format of Oracle SQL Developer, but TDM has more capabilities how import this data to model.
Scripting - Toad Data Modeler can be called from JScript and you are able write script to modify many properties of it.
Modify Model file - Model File is in XML format, so you can simple insert this information to it.
Import From Excel - This choice is not for layout, but you can use it for caption and description.
So problem is how to read information from Oracle SQL Developer.
Import from Oracle SQL Developer is not planned for next version 6.4. Maybe it could be in some next release (before it we need to do some analyze to specify feasibility).