Restore dictionary toolbar handle in Modern style

[vedgy]

Moving dictionaryBar with invisible handle is possible but difficult and
practically undiscoverable.
I can think of two reasons a user might want to move this toolbar:

• increase the width of translate line to the user's liking;
• move dictionary bar to a vertical position like in scan popup.

If a user applies her own tweaks on top of standard Modern style in
user-defined qt-style.css, it is more obvious how to hide this handle
than how to restore it when it is already hidden by the built-in style.

[vedgy]

I don't expect this pull request to be merged into master anytime soon due to this comment. It is here to find a workaround, for discussion and for possible distant future merge.

I'd like to make the handle look like after applying this pull request without modifying qt-style-st-modern.css. After reading this answer I tried to do this by adding the following code into my <Goldendict user directory>/qt-style.css:

#dictionaryBar::handle {
  all: initial;
  * {
    all: unset;
  }
}

Unfortunately this solution doesn't work. Any other ideas?