On a machine I used at my old job, I had a little taskbar app (which I'd configured to be the default browser) installed that allowed me to configure e.g. Slack links to open directly in Slack, and the same for other apps, and all other links to open in Firefox as usual. It helped prevent loads of tabs piling up (e.g. click a link in Slack, it opens a tab in the browser which then opens up some other app, ugh). It essentially acted as a little configurable router for any link clicked in apps.
It worked great, but now I'm trying to find it again and I can't remember what it was called or how I found it. Does anyone else know what I'm talking about?