Hi there,
Your wishlist should be visible on your computer through the Config file. The file itself might be hidden, so you may need to use Admin privileges.
I use Linux mostly, and the Config file can be viewed in the .nicotine folder, once you have keyed in Ctrl+H to make visible hidden files.
In the Configure file, go to the section [Autostart] and remove any items from there, then save the Config file upon exit.
When you next fire up your Soulseek client, the Wish List will be cleaned out, as per the edit on the Config file.
Cheers.