Hi Luke,
Not sure about the manually pasting backlinks in, but I have been using SEMRush for over 3 years and the backlink audit tool section here is really great. It shows you plain and simple your toxicity score and how many backlinks they have analysed. You can also choose to keep or delete links straight from this tool.
It's a pretty comprehensive tool, especially when you consider all the other things available within SEMRush (like position tracking, keyword research, competitor research, traffic analytics, site audit, etc.)
Hope that information helps