How to pass values or data from a page to a webform using webform link field?
Add a webform reference field to the content type and put the default values in

Default submission data (YAML)

and you see this example provided by the field:

# This is an example of a comment.
element_key: 'some value'

# The below example uses a token to get the current node's title.
# Add ':clear' to the end token to return an empty value when the token is missing.
title: '[webform_submission:node:title:clear]'
# The below example uses a token to get a field value from the current node.
full_name: '[webform_submission:node:field_full_name:clear]