adding location by coordinates in a workform

Our customers need to fill a form and specify a location of an event.
We added a location column to the board, so this field apears in the form.
Nevertheless, there are events that occured in a location that doesn’t have a specific address, so we need our customers to type in a geographical coordinates.
We figured out that inside the board (The main table view) we can type coordintes in the location field and then it will be displayed on a map view or widjet. BUT, inside a form the only option is to type an address, because the location field is defined (in a form) as a dropdown list. Inside a form there is no option to type a coordinate like in the main table view.
How can we let our customers define an events’ location using a workforms, for cases that the location doesn’t has an address but only a geographical coordinate?

Your help will be appreciated,