Save progress function with a long form?

I've got a site with a long registration of 8 sections and about 35 fields. Is there anyway to save progress at any point so users don't lose everything if they take too long to complete?

Thanks

We've no support for partial registrations. I'm honestly not aware of any platform having such functionality. The best I'd be able to suggest is something entirely client side that saves what they input into browser storage and restoring that on next visit, but that's something you could implement yourself since it requires no edits to existing core code.

I however recommend keeping registrations as absolutely minimal as possible for best possible conversions. For example if possible only ask what is necessary to establish the Joomla account (name, username, email, and password) then collect other information afterwards. If a field is vital to the sites function then that should also be on the registration form.

Problem is that the client wants to collect all info at once and not have a multi-step process. It's a professional organisation so no conversions needed as prospective members need to join. Not a huge issue but just wondered.

I'm not sure what the issue is then. Are they gone so long their session expires and causes the form token to expire? If that's the case you should be able to just increase the session time in Joomla global configuration.

It isn't an issue yet, and I have a 60 min session, but their current WP site does have this problem and I'm trying to anticipate it.

The only thing I can think of is as suggested earlier. To implement some JavaScript to save their data client side and restore it on next visit. You can insert custom JS to the registration page using CB Auto Actions acting on the onBeforeRegisterFormDisplay trigger with a Code action.