According to https://bugs.gnucash.org/show_bug.cgi?id=798600 value

Changelog message

Transactions with capital gains processing can have splits in transaction currency with a zero amount and a non-zero value. To properly import those, prefer the value column even if transaction currency equals account commodity. Previous (wrong) assumption was that in case of a same-currency split, the amount would always be the value.

Update csv transaction export format to include split values. In the csv importer the 'GnuCash Export Format' option will now include values. For compatibility with filex exported from older gnucash versions the previous preset is still available under the name 'GnuCash Export Format (4.x and older)'.