Is there a way to make a copy of all libraries used in a project and store them as a part of the solution or project? To "freeze it in time" so that I don't have to spend ages figuring out what versions of what libraries worked with a specific project when digging it up after a while ?

Yes we are adding a clone to make this easier. However you can do this quite easily.

Use the add library>always add a project to see how a shared project works. You will see that visual micro creates a .vcxitems (shared c++ project) project file in the lib folder and adds it to the solution.

You can simply copy the library to a new location, remove the project from the solution and re-add from the new location. Make sure the new location is not below the real arduino project. The best combination is the solution in top level folder with libraries and real projects as child siblings.

solution
    libraries
       lib1
    projects
      proj1

Automatic workflows to implement this are included in 1907.26.9 which is currently available in the releases section of this gallery. When you select a library to include in a project the new menu options shown below will govern if the library is copied to below the solution or the current project with or without versioning.

This assumes your solution folder is not the same location as the project, otherwise both options will place libraries in the same place (below the project) in a sub folder called "Libraries".

The name of the "Libraries" sub folder is a new option in tools>options if you want to change it.

https://www.visualmicro.com/pics/Clone-Arduino-Library-Version-Solution-or-Project.png