What problem does this address?

While @helen was streaming recently, she found that when adding social icons to the navigation block that the + button was quite confusing. If you clicked the + button right next to the social icons, you could only add other social icon blocks. If you clicked just outside of the social icons section though, you were then popped back into the usual experience of adding blocks to the navigation menu with more options:

What is your proposed solution?

Not quite sure beyond clarifying what can be added and why perhaps similar to the overall work being done around explaining limitations: #30159

cc @jasmussen for thoughts :)