Can't save D:/Programs/Unreal Projects/UnrealUniverse/Content/Materials/Lake/M_Lake02.uasset: Graph is linked to private object(s) in an external package.
External Object(s):
/Engine/Transient
Try to find the chain of references to that object (may take some time)?
Is this a blueprint project? Ive heard rama say to search for all instances of “Transient” and then remove them.
When I get this error I make sure everything else is saved. Close the editor. Delete /saved/ and /intermediate/ and then restart the editor (and usually I just have to restart the editor)
Hope this helps Don’t forget to accept an answer that best clears your question up or answers it so when the community finds your question in the future via search/google they know exactly what you did to fix it/get it going.
What are the Textures that you are using in your material? Are you using any textures found in the Engine or Plug-In Content? Have you added content from one of the Learn or Marketplace projects to your project? Are you using any textures which have not been imported into the engine correctly (via migrate option) and perhaps just copy pasted into the content folder from another project? Also has the project been converted up to 4.8 or created directly in 4.9?
If you can answer as many of those questions as possible I can try to help narrow down your issue -