Switch to Gitter Next in Franz
Open Franz DevTools. They don't have a UI for that but support team told me that
Ctrl+Alt+Shift+Fn+Upwill do it on Mac laptops. I assume
Ctrl+Alt+Shift+PgUpshold work elsewhere.
Franz is an Electron app. All chat windows are
WebViewelements and you can't inspect them. Select a webview element for Gitter (not the shadow DOM root inside it). Then open a console and type
$0.openDevTools(). This is an Electron API.
To turn on Gitter Next paste
document.cookie='gitter_staging=staged;domain=.gitter.im;path=/;expires=' + new Date(Date.now() + 31536000000).toUTCString()into the console of the new DevTools window. This one-liner is from Gitter Support article.
You may need to restart Franz after that. Enjoy!