It seems that this add-on, like all others, doesn't grab the Channel ID and the orange entries are soft blocks (Channel Name).

When I enter the Channel ID, the entries are gray.

Probably going to have to use Violent Monkey to snipe the Channel ID then paste it on FilterTube's popup menu.

Update:

You don't actually need to parse the whole ytInitialData object or use the API. You can grab the ID directly from the page head using either of these reliable DOM selectors:

document.querySelector('link[rel="canonical"]').href.split('channel/')[1]

document.querySelector('meta[itemprop="identifier"]').content

Since YouTube is a Single Page Application, you just need to wrap these in a MutationObserver or a small setTimeout to ensure the elements have finished injecting before the script fires. It’s light and fast.

Failsafe version that tries both:

const channelId = document.querySelector('meta[itemprop="identifier"]')?.content ||
document.querySelector('link[rel="canonical"]')?.href?.split('channel/')[1];

Not the hero we deserve but the hero we need, this extension is awesome and much smoother compared to other filters. The UI is really user friendly, keep up the good work!