I've been using DOpus for about 15 years and have successfully avoided using a mouse in about 99.9% of my usage. I have all buttons and menus hidden. I'm currently using DOpus 12.20. I'd like to say thanks to the brilliant developers behind DOpus for making this software so keyboard-friendly and adaptable to different preferences and styles of interaction.
After typing into the Filter Bar, hitting Tab makes the focus go to the "X"/clear for the search box and then hitting Tab again puts focus on the file listing.
Maybe it's pointless to have focus on the "X" because it doesn't seem to respond to keyboard input anyway and even if it was controlled by the keyboard it's not useful. For typos, usually normal text gestures like backspace/delete are most useful and clearing the search box to start over can be accomplished with 1 or 2 quick keyboard gestures: Escape and whatever activation gesture is set, e.g. "*".
In other words, the "X" seems to belong to a mouse flow and not a keyboard flow.
So the issue is making the Filter Bar more efficient so 1 Tab press can be used instead of 2 Tab presses.
You should be able to activate it with space or return when it has focus.
I guess the clear button isn’t strictly needed when using the keyboard. On the other hand, some people may be used to using it or the number of tabs pushes to skip past it and might complain if we change it. Will have to think about it, but maybe you’re right.
As far as I can tell, the clear doesn't respond to space or return while it has focus.
Also worth noting that after a Tab press that moves from the input box to the clear, a reverse Tab doesn't move back into the input box.
I feel dumb now, because I just discovered that simply pressing Enter after typing in the Filter Bar box moves the focus to the file list, so using Tab is irrelevant. And perhaps Tab usage is best avoided in general since the behavior seems highly dependent on idiosyncratic variations on a user's Lister layout. (I had been only using the Find tool in DOpus for many years and just tried using Filter Bar for the first time, so that's why I made this naive post.)
I was checking space/enter in our development branch earlier but it seems you're right about the current release version. That's something that will work in the future, although it sounds like the issue is moot now.