Assuming your custom fields are in a separate CSV file, without the Pipedrive record ID, you’ll want to follow these steps to accomplish this update:
1. Export the records (I’ll use people in the example here) from Pipedrive. If you need to update all, you can simply to go Settings > Export Data:
If you only need to import a select number of records, you can create a filter and export from there:
2. Use this exported CSV and your existing CSV with the custom field data and merge those together, so that you have a single sheet with both the Pipedrive record ID and the custom fields you want to import (this can be accomplished by using VLOOKUP - more detail about that here.
3. When you have your CSV ready, you’ll start a new update and on the mappings step, map the record ID and all the custom fields you want to import: