There hasn't been a lot of editorial changes because the major version change has been mostly focused on moving from .NET Framework to .NET Core (.NET 6+).

Originally, the dashboard was removed, but then it came back in a later version of CMS 12. The list property was formally added in and is now supported, but that shouldn't look too different to editors compared to the older version of it.

You could just run through the list of releases since CMS 12 was released to see if anything stands out, but in my mind, there hasn't been many changes to the editor experience.

Most of the editoral changes have come about from the removal of WebForms to MVC as .NET Core doesn't support.

• The admin area has been completely redesigned, it looks similar but is slicker and has filtering is list sections and scheduled jobs have graphs without the need of a 3rd party addon. A few areas were removed/tweaked which you can find detail on here https://world.optimizely.com/blogs/scott-reed/dates/2021/7/-net-5-preview-breakdown--admin-area/ 
• Dashboards were removed as Chris said but are back noiw
• Reports were removed
• Visitor groups were reworked and are faster and slicker now as they are front end driven
• Some editing features are slight tweaked such as adding images, tooltip changes with a help icon (but I'd suggest inline as per here https://world.optimizely.com/blogs/scott-reed/dates/2023/3/restoring-help-text-for-display-name/ )

Apart from that a number of changes will likely be down to migration of your own project

• Any custom editor properties that need migrating
• Any third party packages that don't work as not migrated or built in webforms
• Any admin areas or packages 

It's probably worth considering all the new field options as part of your migration...

public virtual IList<SomeBlockType>? BlockProperty  { get; set; } // Replacement for Property Lists and still exists as part of the main content life cycle

public virtual LinkItem? SomeLink { get; set; } // New for singular links with all properties in one modal.  very nice to use.

[ListItemUIHint(UIHint.Image)]
public virtual IList<ContentReference>? Images { get; set; } // Nice multi image selector

I'd also recommend looking into #nullable contexts with .NET 6+, it's very nice and results in a stronger code base but takes some getting used to.

Blog post showing a few of the (small) editing environment changes: https://world.optimizely.com/blogs/cindy-gilicze/dates/2022/8/3-small-but-helpful-ui-changes-in-cms-12-10/