A number of our clients use multirecord custom data, and over the years they have often struggled with how to add or update that data in bulk. I recently learned that there is an import tool just for multirecord data - but for some inexplicable reason, the link to it is hidden deep inside some help text (where most users would probably never think to look for it). If you click the help text icon for the import wizard, you’ll see the link.
On the import form, you’ll need to select the custom data set to which you’re importing. Also, note that as with other import tools in CiviCRM you’ll need to split your files by contact type. Be sure to include the entity ID for the type of data you’re importing - for example, if the custom data set relates to contacts, include the contact ID.
On the next two screens you’ll be prompted to map your data (just like Civi’s other import tools) and then to submit the import. You can then check the import to ensure everything inserted correctly.
Even though it’s an extra step to import multirecord data separately, this tool should be terrifically useful for those of you who utilize multirecord data sets. If you run into any problems or have questions, reach out to your support email!