Open multiple windows
Being a native macOS citizen, Shrugs.app is not constrained to a single window. Open as many main windows as you want. Peek into threads using popovers and detach them into windows to continue a conversation while the channel discussions keep going.
Markup images and documents
Just like in Apple's Mail.app, you can use macOS Action extensions to modify documents and images prior sharing them. Whether it's the standard markup extension, or 3rd party ones like Pixelmator's repair tool, they'll work in Shrugs.app's compose panel.
Integrate your iDevices
Draw a sketch on your iPad and directly send it to a Slack conversation using Apple's Continuity feature. Scan a document or take a picture using your iPhone.