Use WrapPanel and remove Margin
MODIFY
WalletWasabi.Fluent/Views/NavBar/NavBar.axaml
WalletWasabi.Fluent/Views/NavBar/NavBar.axaml
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
- <StackPanel HorizontalAlignment="Left" Margin="8,6,8,6" Orientation="Horizontal" />
+ <WrapPanel HorizontalAlignment="Left" />
</ItemsPanelTemplate>
</Setter.Value>
</Setter>

Use WrapPanel and remove Margin