Can we get the converter to ignore non-blocking errors?

No. Error messages related to the XBRL taxonomy is specified by the taxonomy, which means that non-blocking error messages need to be included, even if they are in fact non-blocking.

The difference between a blocking and a non-blocking error is that while both are conflicting with a streamlined report a non-blocking error does not bar your report from being approved by the local authority in charge of receiving your ESEF report.