DYN365 Bug: Related Record Filtering not Working on Lookup when source field is in the header
Just a note that i found out that you are unable to filter a lookup on a field in the header. This is a known bug by MS from version 8.2 however i have found this to not be working in v9.0.
The workaround is to put the field on the form and hide it.
Hopefully MS will resolve this in the next release