Is it possible to create (and save) a fluid app with multiple tabs?

Developer of Fluid here. Although there's no explicit support for this, it can sorta be accomplished by:

1. Launch your Fluid App and set up the windows and tabs you would like to appear on launch.

2. Ensure that the following preference is enabled:

   Preferences > Behavior > On startup restore windows and tabs from last time

3. Quit and relaunch your Fluid App, and you'll see the same windows and tabs are open.

So obviously a bit late here, but I found a workaround for those that really want this. You will need access to a HTTP server (it may work with file:// urls, but I have not checked).

What you will do is create a HTML file that spawns tabs with the windows you want to launch, then closes itself.

Steps:

• Add your domain to the whitelist tab, as well as the domains of the sites you want to open.
• In the Security tab, uncheck "Block pop-ups"

• Add a file on your server with the following content. In my case, I used it to open multiple Slack windows (yes I know they support multiple accounts, but this was better for me):

  <script type="text/javascript">
      window.open('https://a.slack.com', 'a');
      window.open('https://b.slack.com', 'b');
      window.close();
  </script>
  <p>Loading Slack...</p>
  

• Link to that file as your startup page.