I m using drop down list in custom fields efficiently since long.
Now I see drop down list option in line itmes i.e sales invoice. When I start using drop down list option in line custom fields it is not working in line items fields.
Currently, custom fields won’t appear on line items anything other than plain text fields. Even if you configure them to be dropdown list. This feature is coming soon though.
Which version of Manager are you using? You now can use Multiple Value Custom Fields, see screenshot taken from Manager v23.5.8.822. Note that custom themes may not work with these new features as they are for more than a year obsolete features waiting for a new implementation.
This is a long-time awaited Feature - Using drop down lists in line items !Plz @Lubos, this is a great feature for adding value to the Custom field functionalities.