It may be that the rectangular buttons make sense for horizontal button groups, but this a vertical button group (see zoom in/out controls), which doesn't exist yet. That said a labelled vertical button group should probably have the same padding as normal buttons...

We should definitely take into account touch target size consideration which is currently baked into the width of buttons, which in turn lead to rectangular icon-only buttons with exception of NumberInputWidget, which is a special case, as it's possible to interact with it without using the buttons and CapsuleMultiSelectWidget, which is a special case as it uses an indicator-only button, that should be [[ T150071 | removed/replaced ]] for exactly that mobile-problematic reason of not providing a sufficient touch target size.

In T161601#3136705, @Esanders wrote:

It may be that the rectangular buttons make sense for horizontal button groups, but this a vertical button group (see zoom in/out controls), which doesn't exist yet. That said a labelled vertical button group should probably have the same padding as normal buttons...

I agree, in a vertical button group a square makes sense. It could maintain the current width and set the same height to ensure accessibility.

Google Maps	Leaflet

Our buttons should probably be larger than this.

This has also cropped up in the NumberInputWidget: https://gerrit.wikimedia.org/r/#/c/352470