Whenever migrating to a different password manager an important thing is exporting all of the data. Unfortunately, most of the password managers export by default to csv or support importing from csv only. Exporting everything to a csv with 1password contains only the default fields (such as username, password, notes), but won't export all the custom fields (e.g. fields that it suggests to add for a passport, any imported SSH keys etc.). I created those functions in order to easily manage my items that have some additional information than what can be exported to a csv file.
In order to get the file, you need to export the 1password account to .1pux file (1password unencrypted archive). Then change the file extension to .zip - inside there is the export.data file with a dump of the whole account.