Ctrl+E: Focuses the filter textbox
Which one - the database or the table filter box? And why "E"?
Esc: Clears and unfocuses the filter textbox, but only when the filter textbox already has the focus.
You cannot "unfocus" a control. You need to focus just another control to do that. So, which one shall then be focused? To be honest, I feel focusing another control would be quite non-intuitive, as it's mostly not the control the user wants.
Ctrl+Shift+E: Clears the filter textbox regardless of which control currently has the focus.
Makes sense, I guess then for both filter boxes. Only I find this "E" not quite the right character for removing a filter. But anyway, the user can customize the shortcuts, and Ctr+Shift+F is already in use by "Search text on server".