In the quotes/invoices rows, the first field/column is the article reference (aka item). Why is this mandatory ? Why if nothing is typed in this field, the line is not saved without any error message ?
As any value can be typed i, why not allowing a null value ?
No one has an idea about that ?
You could turn this off if you wish. The ‘item’ field in the invoice item maps to the “item_name” field on the database, which does allow null values.
However…
On the printed invoice, you should be printing a readable description of what the item charge is for. There are two fields for this - item_description and item_name. Both should not be null, as this makes for a not so useful line item.
The item name is normally copied from the product selection popup, so it would therefore make sense to make that as mandatory, I would think.
Cool, that’s what I thought … but I needed confirmation. 
Yes, but no. This is my experience (from +200 clients using another tool) that the item reference, in many configuration, is not wanted (for small companies that do not operate using a catalogue of items). So what is really mandatory is only the description (item_description). And if you use a reference, there must be a description in your catalogue for the reference.
If you are using the Add Product button, yes on that popup, the item reference should be mandatory but you can only choose an item from the catalogue … so the item is reference is mandatory then.
However, if you choose the Add Row button, then there is no reason why you could not enter directly a description for an item not in the catalogue.
At the moment, the fact that if you do not enter a reference, the row is not saved without any error message is very disturbing at the least, because if you have typed in many rows, and only one without reference, you may NOT notice that this row was recorded.
Any how, thanks for the answer, I will make the reference not mandatory for me.