The VMWare Tools necessary for shared folders do not work.
Use open-vm-tools (https://github.com/vmware/open-vm-tools/wiki/FAQ#installation).
After installing open-vm-tools and rebooting the system, you can find the shared folders at /mnt/hgfs.
That triangle is there because Fusion is not being told by the guest that the "legacy" VMware Tools are installed. That's apparently by design, because open-vm-tools do not indicate that they are installed back to the host The reason for that is that open-vm-tools are not managed by the host. They are managed by the package manager in the guest.Because Fusion isn't told that the "legacy" VMware Tools are installed, it throws that warning triangle. It can be ignored if you have open-vm-tools installed in the guest. I wish they'd fix that, but it's an annoyance that I can lived with once its understood what's going on.
The shared folders mount point should be visible in the VM on /mnt/hgfs, with your shared folders being subfolders of /mnt/hgfs. Dropping into a shell prompt and issuing a 'mount' or 'df -k' command should show the shared folders are mounted. If there's no mount on /mnt/hgfs in the VM once the folders are enabled on Fusion's side, disable, then re-enable the shared folders in Fusion. They should then appear. That's where the more persistent workaround that's in the release notes and/or the Unofficial Guide are helpful.
(By the way, most Linux file managers don't recognize the folders are mounted,. You have to manually navigate to the /mnt/hgfs folder.and perhaps set up a sidebar shortcut to get there).