From what you’ve described so far, it’s the Group datatype (not the User datatype) that you want to make changes to.
I would agree with what the others have said in that keeping the whole process on a single page is a much better way to go - it will be simpler to create and change the Group, and much better/faster UX for your users.
There are basically 2 primary ways to to what you want to do on a single page:
Create the new Group in the first part of your form, then make changes to that group in all subsequent steps.
Just create the Group once you’ve collected all the information you need in all the steps of the form.
Personally, I would probably opt for the second option, to keep things simple, although either option should work if you’re keeping the whole thing on a single page (if not then you’ll need to use the first option).
If you decide on option 1, here is a basic outline of the process:
One of the parent groups on the page should have as it’s content type Group, with no defined datasource to start with.
Once the first stage of the form is complete, and a button is clicked to move to the next stage, use a workflow action to create a new Group, with the data from the first part of the form. Then, in the same workflow, use the element action ‘Display Data’, to set the datasource of the parent group to be the newly created group - i.e. the results of step 1.
Then, in all subsequent workflow steps, you just need to use ‘make changes to a thing’ and refer to the parent group’s Group as the thing to change.
You can use the exact same method if you decide to use multiple pages, but you’ll need to send the newly created Group data to each subsequent page (as mentioned in a previous post, you’ll need to set the content type of those pages to be Group).
Alternatively, you can just leave all the input data in the inputs, and use a single workflow action at the end of the final stage form to create the new Group, and all all the data from all the inputs, then reset the inputs ready for the next new Group.
There are always multiple ways to do things in Bubble, so there are probably even more than I’ve mentioned here but, as I said, personally, for simplicity, I’d probably just use a single workflow action to create the group at the end of the whole process - but it really depends on your specific use case and desired UI/UX as to which approach would be best for your app.