In order for our plugin to see your field, it must be created ONLY in the Lead. If you create a field in the Lead, then convert the Lead into a Deal, then Bitrix24 will automatically create the field in the Deal and "link" it with the field in the LEAD. Thus, our plugin will transfer information in the Lead field, and Bitrix24 will create a deal and automatically transfer this value to the Deal. How to do it:
1. Go to CRM Settings, Field Settings, LEAD and create the required field.
2. Create a new Lead through the site, for example, by filling out a form or placing an order, and check how our new field works.