Hello @mkt ,
The best way to do this is to create a new tag and tag users via CSV File.
Article from Intercom help center:
Can I update user data with a CSV import?
Yes. You can update values, and add new attributes for existing users. All CSV imports require you to have a column with user email addresses. A few things to note:
You can update the email of a user by sending the same user_id and different email address. We'll update the user with that user_id in Intercom to reflect the new email address.
You can't update the user_id by setting a new value for it and using the existing email address - that would create a new record.
If you use both user_id and email in Intercom, sending email in a CSV import is enough to match the user record in Intercom.
If you leave a field blank when updating existing columns, it will result in overwriting values to unknown .
More information can be found here.
Let me know if you have any further questions about this topic, more than happy to help.