All 3rd party apps require knowledge of the .iif file format and specifically the header. There isn't much help online either by QB/Intuit or others as most use Desktop versions of the software. The biggest issue is that the Budget is a List. Even with 3rd party import tools - there's no way to create a new Budget List (eg: FY19 - High vs FY19 Low versions of same fiscal period budget).
Very frustrating. Even an export .iif option would provide a significant improvement level over current functionality. For customers like me who have >100 rows in my COA and budget multiple times year on a high and low basis across multiple Classe - it's ridiculous to think I'm going to manually type in literally thousands of points of data.
It would even help if a user could copy past on the budget creation fields from an external source! The idea of copying a single amount across all fields (current functionality) in a row is ridiculous.