Hi Markus,
Trials come as is, there is no chance to alter the system that is provided. Even if you would have an SAP license for it, installing that license would violate the terms and conditions.
For sure I know this will not help you solving your issue. However the good news is, that a new version of the ERP Foundation Trial is currently worked on. I've asked the team if they would be able to take a look at your issue and maybe fix it in the new version.
Regards,
Hannes