Windscribe doesn't include split tunnelling unfortunately. It was brought up on Reddit years ago and they claimed it was on the roadmap but it's never been implemented.
You might try tweeting at them or creating a feature request on Reddit about it, but I wouldn't hold my breath if I were you.
What kind of applications do you want to run on? For example, if you use NordVPN you can encrypt only browser traffic with a browser extension, set up a proxy on torrent clients or just use an app for the whole connection. Don't know about Windscribe much.