"pinned" tabs alternative?

Folks;

I'm looking into (and actually enjoying) epiphany as a lightweight web 
browser alternative on my GNOME desktop yet so far am missing a feature 
I haven't really managed to get replaced here: In my environment I'm 
supposed to use Slack and some other web apps that should be open all 
the time, which (on Firefox or Chrome) I have been done using "pinned" 
tabs that started with the browser and were always "open". In Chrome, as 
an alternative, I could allow these pages to send desktop notifications, 
leave Chrome running in background and even close the browser window, 
still being sure I don't miss any relevant notifications.

In epiphany, lacking both features as far as I can tell, is there a 
"preferred" way of doing this? I don't want to install the heavyweight 
Slack desktop client again as, if doing so, I might as well stay with 
Firefox or Chrome and won't have any benefits in using a more 
lightweight browser... ;)

Thanks in advance and all the best,
Kristian