[WASM + Material] How to change the width of a ScrollViewer 'slider'?

[DierkDroth]

I wonder if and how I could change the width of the ScrollViewer slider. Reason: on WASM the slider looks very different than on WindowsAppSDK/WinUI3. I checked the Material sources in the UNO themes repo but could not find any hint.

In UNO theme sources I found this:

<Style x:Key="ScrollViewerStyle" TargetType="ScrollViewer">
...
     <Setter Property="Template"
        Value="{StaticResource ScrollViewerScrollBarlessTemplate}" />
    <not_win:Setter Property="(uno:ScrollViewer.ShouldFallBackToNativeScrollBars)" Value="False" />

... but I could not find any reference on ShouldFallBackToNativeScrollBars in the theme sources not would I know if this is the right starting point for my research.

This is WinUI3:

And this is UNO WASM - note the difference, in particular on the width of the slider

Any hint would be appreciated