Hi @Leo, if one day you can, evaluate the possibility of enriching the Filter field similar to the Filter bar, thanks.
The filter field is a legacy thing which we're only maintaining, not actively adding new things to.
The Filter Bar is where our focus is, and what we recommend using.
What a pity, I prefer the filter box, than the bar, the bar occupies the entire width of the screen and in the end it provides few elements, some of them repeated, such as the number of files and folders, which normally exist in the Status bar .
And have you never thought about the possibility of being able to edit the Filter bar as we do with the Status bar?
And PDF files, apparently you don't consider them documents, because you don't include them in the "Documents" group of the Status bar.
Thank you!
When we have the Filter bar set to only show when editing a filter, we can quickly show it with Set QUICKFILTER (toolbar button), but is there a way for a button to toggle between showing/hiding the bar?
Good to know that I'm not the only one who dreams of these possibilities, who knows and one day they attend to our requests 
Hello @Leo yesterday you told me that you do not have in mind to modify the Filter field, but until today I am wondering why it would be so difficult to apply the recommendation that I am asking you with so much love and respect.
You would not have to do anything new, you already have the code in the Filter bar, it would only be extended to the Filter field, and that does not detract from the value of the program, quite the contrary, I think it perfects it even more, to the best Explorer files of the the world! 
You can edit the file type groups via Settings > File Types.
It’s normally only on screen when filtering, at which point most of that extra functionality (including what you’re asking for) is useful and worth some screen space.
The counts aren’t the same as what’s on the status bar, and can be clicked to see/hide all files/folders.
It’s all useful, and is hidden when not needed. Cramming it all into a single small field (that itself uses space even when you aren’t filtering) wouldn’t work well.
We aren’t getting rid of the old field, but it is what it is. A much more simple UI compared to the fuller one.
Thanks @Leo for your comments, I included the extension .pdf in the Documents file group and these files are now considered documents in the Filter bar. I knew about the importance of file groups, for, among other things, applying Folder Formats, but I didn't know that these affected the file count in the Filter bar, everything is well integrated, congratulations! 
Regarding the Filter bar, between what you explained to me and everything I read in depth in the Manual, I was convinced that each detail, each component has a logical reason for being, for being there, excuse my ignorance, you know the program with a lot of mastery, you are a sniper with your words.
I only make one last recommendation, with great humility, to allow you to customize this bar in the future, in the sense of being able to incorporate new elements into its free space, or to be able to place it on the top, side, etc., or even to be able to located within the same Status bar {filter}. If one thing characterizes Directory Opus, in addition to its versatility and power, it is its high degree of customization, the main reason why I am recommending it to all my friends.
I don't want to talk more about the Filter field, apparently, nor am I going to convince you to enrich it with check boxes and number of files, nor are you going to convince me that it's good that it stays as simple as this. 
Very grateful @Leo for everything!