Rouler

Rouler is a Windows utility for steering network traffic across multiple network interfaces. It routes traffic by application or IP address, so different apps can use different connections at the same time. Rouler is VPN agnostic and works with any tool that creates a Windows network interface.

For example, you can run the Tailscale, Mullvad, and OpenVPN official clients simultaneously. You could send Slack through OpenVPN, Chrome and an IP range through Tailscale, and a torrent client through Mullvad. Rouler describes its approach as "rules for your routes."