Could you try this plugin: https://www.dropbox.com/scl/fi/aod0ragyfqoc1ogk0gu1x/wph-vipps-complete-form.zip?rlkey=ts63jkbfwnjtoob4g7ue31zee&dl=0
It’s a bit rough but should be fully functional and can at least be a basis for further work. Basically, you will need to add annotations to your CF7 fields of the type “vipps:name” “vipps:email” to the fields you want to be auto-completed, and then add a “complete this form” button either using the Vipps Login Block or a shortcode. See the readme for details.
Unfortunately, it isn’t possible to do this in an iframe, so the page has to be reloaded to complete the form. I’ve tried to make sure any fields present will be saved and restored on the reload.
Sorry it took a bit of time; I had to research the CF7 plugin a fair bit to understand how that worked.