Is it possible to subdivide scale bar segments in QGIS?
There's a few steps involved:
Create your first scalebar showing kilometers and set the relevant options:
Select the first scalebar and copy/paste it below the original and set the relevant options:
For the copied scalebar, set its
Font colour
to have an opacity of 0%:Item Properties > Fonts and colours > Font colour
Move the copied scalebar and align it to match the original scalebar. Select both these scalebars and group them:
You should hopefully have a scalebar with subdivided segments:
The feature is available in the current QGIS Master 3.13 and in the forthcoming release of QGIS 3.14:
See https://github.com/qgis/QGIS/pull/36131 and https://github.com/qgis/QGIS/pull/36222