To be removed from a group DM in Slack, the remaining members must create a new group chat without you or a private channel. If this is not an option, here are some steps you can take to hide the group and stop receiving notifications from it.
1
In the sidebar menu, right-click on the group DM you want to leave
2
Click "Mute conversation"
3
You will no longer receive notifications from this group DM
4
Right-click on the name again
5
Click "Close conversation"
6
The group DM will disappear from your DM list
Note that even if the group is no longer visible, you are still part of it and can re-join at any time, as the next steps will show.
7
Click on "+" next to "Direct Messages" in the sidebar menu
8
The group DM will be listed. Click on it to re-join the conversation
9
Type a new message
10
The group DM will reappear in your DM list
