Could you provide more information on how the relationship in the Table Occurrence Graph is setup between Software and assignments. Which fields are the join based on and what the field contain.
vendor table: pk vendor, fk employee, fkLicense
Software table: PK license, fk assignment, fk vendor, fk employee
Assignments table: pk assignment, fk license, fk vendor, fk employee
Employee table: fk assignment, fk license, fk vendor, pk employee
pk vendor (vendor table) linked to fk vendor (software table)
pk license (software table) linked to fk license (assignments table)
pk license (assignments table) linked to fk license (employee table)
The portal you put on the software-layout should be the table occurence assignment and in that portal you should place a field from the employee database ... it should work fine ..... However I think it is a bit of an odd datamodel (sorry) and I think that your aim is to enter the softwarepackages from a certain vendor only once and that you would like to enter the employees also only once. You probably want to keep track of the licenses of software that are in use by the different employees.
That in mind you may change the model as follows:
pk vendor (vendor table) linked to fk vendor (software table) [the same]
pk license (software table) linked to fk license (assignments table) [the same]
fk employee (assignment table) linked to pk employee (employee table) [changed]
On your layout with software as base table you need to place the portal with the assignment table occurrence and on that portal you can show fields from the employee table.