+ AA6YQ comments below

How can I create an ADI file including only QSOs that have entries in the SOTA_REF field?

+ Filter the Log Page Display with the SQL expression

LEN(SOTA_REF)>0

+ Then click on the Main window's "Export QSOs" tab; when asked if you want the filter remove, click the "No" button.

+ Set the Options panel to "Export standard ADIF", and click the Start button to initiate creation of the ADIF file.

73,

Dave, AA6YQ