Issues with library on external device and import history

I have a problem when importing playlists. The tracks in these playlists change their location in my collection when I import them from a USB drive. From that moment, the Engine looks for them in the drive from which I imported the playlists instead of their original location, which is what I need.

I also find it frustrating that when the device with the library is not connected, the tracks don’t just appear in red, they don’t appear at all. This is a big problem because in very long tracklists, it’s difficult to see if something is missing or not. Other times, the tracks appear in red. What does this depend on?