Yes, it's certainly possible. One method is by import. You can import the records directly from the ODBC source, or you can set up an ESS occurrence on your Relationships Graph and import from that TO to an internal FileMaker table.
Another method is to set up a relationship between the ESS TO and an internal FileMaker TO and use either lookups or Set Field script steps to copy the data across. Depends on your workflow and exactly what you're trying to accomplish.
But as I like to tell my customers, "It's software. You can do anything."
Mike describes two ways to do it from inside FM
In addition it can be done from the other database too, using the FM ODBC drivers and a DSN for the right FM file; the other database can create, delete, update FM records.
Thanks Mike and Wim,
You have clarified my question. The most suitable approach to my scenario is the one described by Wim, since I need "live creation" on a FM table from an external ODBC client. So I will start now the process of setting up all the required infrastructure to accomplish it (drivers, DSN,...)