My FR in one pic:

It's impossible now to update Ignore list with GUI if nodes are already added to NPM.
In some cases, you may see them (these "undesirable" nodes) only after discovery import - if you have setup an autodiscovery with autoimport.
I had the case and I hate it. I had to remove "undesirable" nodes (>500) from NPM and then re-run my discoveries (>20) in a manual mode and then check Discovery Results for those nodes.
I prefer to fill ignore list in advance. It would be especially useful to use name masks as filters.
Also It's impossible to update Ignore list via API neither.
Correct me if I'm wrong. At least, I couldn't find a verb for that.
Also it's just uncomfortable when you are not able to manage any list as you wish.