The user should have the possibility to navigate/expand/popup the same section(shared information) across different pages

## What needs to be solved?
Some forms require that the user shares same set of information across the form (link to different object spread across different pages) which means that the same information needs to be reused across pages/sections/groups in the form.
F.ex A : List of phone numbers b:List of persons c: List of address. List A is shared across different pages and linked to different object. F.ex The user fills in the form and page 1 he fills the person details and he links phone 1 to person 1,3,5. Then he navigates to page 2 and fills in all addresses and now he has the need to link address1 ,7,9 to phone 2.
In such a case, we want the best possible user experience. In the real life scenario, the phone object is a complex object with f.ex 30 fields and with many repeating groups nested inside. So how can we best solve this user experience issue?

## How do you want it solved?
I think that a popup with many pages can be a possible option for making it easy for the user. So the user can click when he needs a new phone object, he can click add on page 2, person 2 section or he can add when required f.ex when adding information for person10. I would like to present this problem to the UX and agree on a best possible user experience

## Alternative solutions

## Additional context
This issue is raised in relation to a specific requirement to MT-3 form Altinn/apps-backlog#5
F.ex in the picture below, the user needs to link a persons information with an activity/card/account etc. The user needs to have the possibility to add a new person if the list does not contain the person he needs to link to. So the person list must be available across different sections/pages in the form without creating multiple copies of the same information.

No files, tests, or entry points are named. Start by reviewing the issue examples, image, and related MT-3 requirement in Altinn/apps-backlog#5, then work with UX to define the shared-information interaction across pages; done means an agreed user experience and implementation scope.

Written by the indexing model from the issue text.