In Panorama 6, you could get a lookup( to default to the current field if there was no match by using the field name as the default value.
field myField FormulaFill lookup(database, keyfield, keydata, datafield, myField, level)
It is reported that this doesn't work in Panorama X, maybe it is evaluating the formula from the lookup database instead of the current database? Though the default value is evaluated entirely separately from the lookup itself, so that seems odd.
This may be related to issue
#703 but I think it is different, hence I have created this new issue ticket.