Actually, also need to add Child Note as Attachment File Type.

Thank you for pointing this.
I just mentioned this because Child Note is an Attachment File Type (in my understanding), so I was expecting to find it in the list of possible choices as: Attachment File Type is Child Note.
Both searches give the same results, but that does not mean that one of them should be removed. It is the same as searching for notes with the following two equivalent ways:
- Item Type is Note
- Note contains blank
A blank search is working of course, but the first way to search would be more logical to me if I want to see all the notes in my library.

I would also expect to be able to search for Attachment File Type is Link. I am not sure if there is another way to search for all links? One link was returned when searching for Attachment File Type is Web Page. But I could not explain why, as none of the many other links in my library appeared in the search results.

Other remarks:
- If I search for Child Note contains blank, I get only the parent items displayed. I guess that searching for Child Notes should expand the parent items and highlight the child notes as default, so that we can see the result of the search faster?
- If I put the Advanced Search window in full screen, pressing + or - to add or remove the search condition, it exits the full screen mode.
- It seems that a search inside the Title condition does not search inside the Titles of Notes and Child Notes. That may be the intended behaviour. But I am not sure how to search inside these note titles then? One example where it would be useful is when someone uses a systematic naming convention for notes, like in this post.

Zotero 7.0.0-beta.37+075457be4 (64-bit)
Windows 10