Hey @barb55, thank you for your questions.
Yes the values from custom post fields can be retrieved from them with our plugin. You will find them back in the source fields.
If it is not listed out of the box you should add the metakey of the custom post field to the third party attributes” field you find in the settings tab of our plugin.
To find the correct (meta)key if you do not already know it:
1. Create on new product and add a value in the “ecr-gtin” custom field.
2. Check your database and go to table wp_postmeta (with phpmysql for example)
3. sort the table on meta_id Descending
4. The top meta_key would be the meta_key from your custom product field.
If you have found the meta_key, you can make a filter string like %meta_key% (only the prefix of the key) that should be added to the “third party attributes” field you find in our plugin settings page. After that, you find the field in the source dropdown in the feed editor.