It is not possible to create, open or modify saved *.logicdata files.
This is because the files are generated with boost binary serialization, and contain a very complex object structure. In truth, we don't even understand how it works - boost serialization is extremely complex.
If you need to get data out of the logic software, we recommend using the export features. You can find more information in our users guide here: Saving, Loading, and Exporting Data
There is currently no way to get custom capture information into the logic software. If you are trying to add content that is produced from an analysis of the capture, you may want to consider our analyzer SDK to create a custom protocol analyzer: How do I develop custom analyzers for the Logic software on Windows?
trello ID: 55f7002b6041649bffc295e0