Steps to reproduce :

- create a windows folder on the desktop
- name that folder the longest name possible that windows allows
- now create a new folder in Unity
- copy the long name from the windows folder and rename the Unity folder with that name
- notice the first error :

Failed to create folder
UnityEditor.DockArea:OnGUI()

- create a new script and rename it also with the long name and notice the second error
- also notice that the script is now invisible in the project browser

DirectoryNotFoundException: Could not find a part of the path "C:\Users\Marek\Documents\New Unity Project 16\Assets\Standard Assets\1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234.js"

*note :

Following the Windows folders workflow, when entering a very long name the characters should stop at one point not allowing the user to enter more letters.

Also, the problem becomes more visible for hierarchies of folders, where a long top-level folder name affects the allowed length of child folder names (seems like we limit the allowed name length based on total path length?).