Make the toolbar respond to my new breakpoints

In the Drupal 8 theme guide the definitions of breakpoints is quite good covered - but it seems like its lacking how to use them, or perhaps I'm looking in the wrong place.

I made a THEME.breakpoints.yml

THEME.mobile:
  label: mobile
  mediaQuery: 'all and (max-width: 489px)'
  weight: 3
  multipliers:
    - 1x
THEME.narrow:
  label: narrow
  mediaQuery: 'all and (min-width: 490px) and (max-width: 734px)'
  weight: 2
  multipliers:
    - 1x
THEME.medium:
  label: medium
  mediaQuery: 'all and (min-width: 735px) and (max-width: 979px)'
  weight: 1
  multipliers:
    - 1x
THEME.wide:
  label: wide
  mediaQuery: 'all and (min-width: 980px)'
  weight: 0
  multipliers:
    - 1x 

It results that the toolbar is "normal" only for wide - and turns "mobile" on all other sizes. I guess that "wide" and "mobile" is predefined and my new breakpoints is ignored. For some reason it defaults to "mobile".

My question is - how do I tell the toolbar how to use my new breakpoints?

I have tried to make a THEME.breakpoint_groups.yml file, but that did not help:

group1:
    label: Group 1
    breakpoints:
      - mobile
group2:
  label: Group 2
  breakpoints:
     - wide
     - narrow
     - medium