This appears to be a recent regression. I can't reduce the width of the toolbox two just two icons wide. Might be related to the recent removal of the lock/collapse icons.
Yes... The minimum widht has changed, but it's still two icons for me, though.
Git commit 01ac6bbd4b87213c8efdbf2ead89fd79adddcf23 by Boudewijn Rempt. Committed on 02/04/2018 at 12:47. Pushed by rempt into branch 'master'. Set a minimal label as the toolbox docker titlebar widget This makes the minimal width of the toolbox 16 pixels, and makes it possible to drag the toolbox out. It doesn't have close or float buttons, though it's still possible to close the docker. M +12 -1 libs/widgets/KoToolBoxDocker.cpp https://commits.kde.org/krita/01ac6bbd4b87213c8efdbf2ead89fd79adddcf23
Git commit abdd4d7008f8d4cbc9cfccea96788a72b48af2d4 by Boudewijn Rempt. Committed on 03/04/2018 at 11:20. Pushed by rempt into branch 'krita/4.0'. Set a minimal label as the toolbox docker titlebar widget This makes the minimal width of the toolbox 16 pixels, and makes it possible to drag the toolbox out. It doesn't have close or float buttons, though it's still possible to close the docker. (cherry picked from commit 01ac6bbd4b87213c8efdbf2ead89fd79adddcf23) M +12 -1 libs/widgets/KoToolBoxDocker.cpp https://commits.kde.org/krita/abdd4d7008f8d4cbc9cfccea96788a72b48af2d4