Steps to reproduce:

Subscribe to and make ETRT: Medicine Production part of the mods.

Save current list.

Find the file for the current list, copy it all to the clipboard.

Import Modlist From String (clipboard)

The line corresponding to the error is for the mod "ETRT: Medicine Production", I suspect the colon has special meaning while being parsed but it isn't intended to be so in this case.

PS you can find the stored XML lists in different locations depending on your OS:

https://docs.unity3d.com/ScriptReference/PlayerPrefs.html

macOS ~/Library/Preferences/unity.Ludeon Studios.RimWorld by Ludeon Studios/ModLists ???

Windows, ... This depends on a registry key, someone that uses windows would have to say.

Linux, ~/.config/unity3d/Ludeon Studios/RimWorld by Ludeon Studios/ModLists