increase header font size
MODIFY
WalletWasabi.Fluent/Styles/DataGrid.axaml
WalletWasabi.Fluent/Styles/DataGrid.axaml
</Style>
<Style Selector="DataGridColumnHeader">
- <Setter Property="FontSize" Value="{StaticResource FontSizeH7}"/>
+ <Setter Property="FontSize" Value="{StaticResource FontSizeH6}"/>
<Setter Property="FontWeight" Value="Bold"/>
<Setter Property="Padding" Value="12 10 10 10"/>
</Style>

increase header font size