User-Defined Allow Fields are like spices. Similar to specific combination of spices that create a unique flavor, the way UDFs are implement is tailor for each business. Key advantage of UDFs is their great flexibility. UDFs in document rows allow become a seamless part of the document which is of course a benefit. However in sometimes it is require that UDFs would behave differently. For such use cases, SAP Business One introduces a new level of flexibility by allowing to edit. UDFs in document rows regardless the document status or row status:
For each document type, you can choose whether to open the UDFs in the document rows for editing while the document rows are not editable. For example: