For example: User 1 completes Webform 1 on Drupal to give details of a volunteering project, which when submitted creates an activity on CiviCRM.
An email then gets automatically sent to User 2 with a link to Drupal Webform 2 for them to fill out different details relating to the same volunteering activity, which when submitted, data gets added to the same activity that User 1 created on Civi, rather than creating a whole new activity.
I have read similar questions and answers but we are not working with CiviCase and I'm a Civi newbie so finding it hard to relate these solutions to our problem. Apologies if this is a bit of a basic issue but any help would be much appreciated.