To get the Label GUID, you’ll need to have already “searched” using a module from the same app that does searching for existing Leads, OR you’ll need a trigger module that passes in the Lead.
Do you already have such a module in your scenario? If not, see which one suits your requirements here https://www.make.com/en/integrations/pipedrive
Looks like you’ll need to get existing labels from the same lead, and append the new label to the list of labels.
Do you already have a module that contains the existing Lead data? If not, see which one suits your requirements here https://www.make.com/en/integrations/pipedrive
If you need further assistance,
1. Scenario blueprint
Please export the scenario blueprint file to allow others to view the mappings and settings. At the bottom of the scenario editor, you can click on the three dots to find the Export Blueprint menu item.

(Note: Exporting your scenario will not include private information or keys to your connections)
Uploading it here will look like this:
blueprint.json (12.3 KB)
2. And most importantly, Output bundles
Please provide the output bundles of the modules by running the scenario, then click the white speech bubble on the top-right of each module and select “Download output bundles”.

A.
Save the bundle contents in your text editor as a bundle.txt
file, and upload it here into this discussion thread.
Uploading it here will look like this:
bundle.txt (12.3 KB)
B.
If you are unable to upload files on this forum, alternatively you can paste the formatted output bundle in this manner:
-
Either add three backticks ```
before and after the code, like this:
```
input/output bundle content goes here
```
-
Or use the format code button in the editor:

Providing the output bundles will allow others to replicate what is going on in the scenario even if they do not use the external service.
Following these steps will allow others to assist you here. Thanks!