Perhaps someone will come along that understand what you are saying, but it will probably enhance you chance of being replied to with something useful if you invest just a little time in explaining what it is you are trying to do here. There appears to be some sort of conflating of folders, relevance and filtering in this topic but how they are supposed to relate is far from clear to me.

I need to filter mails in the "Unified Folders" -> "Inbox" (and not doing this 10 times, as I have at least 10 email addresses) which are NOT Favorites. Now, I can only filter only those which a Favorites. If I am not makin a mistake.

Those which are filtered I will Archive them. Maybe 30-40 every days.

Is it simpler?

There is no filtering on the unified folder as filtering is undertaken per account and the unified folder is not only not an account, it is really a virtual folder, so it does not have any content as such.

1.) "There is no filtering on the unified folder" - sorry to say it, but it's not true. There is a way to filter the unified inbox filter, small buttons at the top: Show only unread messages Show only starred messages Show only messages from people in your address book Show only messages with tag on them Show only messages with attachment

All the unified mails are in one list on my screen with the buttons above. You have to click on the Unified folders

  Inbox line

in the left column which will show in the second column all the mails and at the top the filtering buttons

My columns (4) on the screen from left to right are, maybe use are using a different view of the application:

1. column name of the folder (ex. archives) - Name of type of group (ex. Unread folders, Unified folders, Tags, All folders)

Unread folders

  mail account 1
  mail account 2

Unified folders

  Inbox <-Click here and you will have in the 2. column ALL mails from all accounts - unified in 1 list
     mail account 1
     mail account 2

Tags ... All folders ...

2. columns Header "Inbox" (name of the folder you are using, might be also Drafts, Templates, Sent, Archives.....) + quantity of messages + quick filter + Message display list options button Mail list

  first line: 6 buttons and 1 message filter field
  body contains the mail list as selected in the 1. column, described above

The application has the following settings: Menu -> View -> Layout OK: Vertical view OK: Folder pane OK: Message list header OK: Message pane

This Thunderbird system will filter on ALL mail and not by 1 account as is in your answer: "filtering is undertaken per account" This is not true in this case.

So: unified inbox might be filtered in five ways already. There is filtering on starred message, but not on NOT starred message.

I do not want to make any advice about how to manage this issue.