Will it still be possible to view the folders and files, in both directions, between a Macbook Air running OS 26 and an older Macbook Pro running OS 10.11.6, El Capitan?
MacBook Air 15″, macOS 15.7
You can't use iCloud Drive. That now requires macOS 10.13 (High Sierra) or later, so only the MacBook Air running macOS 26 (Tahoe) would be able to access it.
System requirements for iCloud - Apple Support
Target Disk Mode and its Apple Silicon counterpart (File Sharing from a special startup mode) wouldn't really help – even if you could meet the requirements, only one computer could be active at a time. The other would be started up into a mode where it was acting as nothing but a disk or a network disk.
You might be able to set up File Sharing on both machines and then have each machine mount the other machine's shared drive area as a network drive.
Set up file sharing on Mac - Apple Support
Connect your Mac to shared computers and servers - Apple Support
You can't use iCloud Drive. That now requires macOS 10.13 (High Sierra) or later, so only the MacBook Air running macOS 26 (Tahoe) would be able to access it.
System requirements for iCloud - Apple Support
Target Disk Mode and its Apple Silicon counterpart (File Sharing from a special startup mode) wouldn't really help – even if you could meet the requirements, only one computer could be active at a time. The other would be started up into a mode where it was acting as nothing but a disk or a network disk.
You might be able to set up File Sharing on both machines and then have each machine mount the other machine's shared drive area as a network drive.
Set up file sharing on Mac - Apple Support
Connect your Mac to shared computers and servers - Apple Support
FWIW, I can share files between a 2010 MacMini with macOS 10.13.6 by just setting up file sharing over my home network. The Mini is actually used as a home server.
On the older Mac, set op what ever folders you want and enable sharing on them. Be sure, however, that all file sharing preferences on the old Mac are set to SMB protocol. I believe macOS 26 no longer supports AFP, which is an old Apple network file transfer protocol.
Then there's an option of using an external USB hard drive, SSD, or flash drive to move files between the two Macs.
The drive could only be plugged into one Mac at a time, and it could not be formatted using APFS (since El Capitan predates APFS and does not understand it).
I think my seeing the files on both computers from each other now is using file sharing. That’s the OS 15.7 with El Capitan. Does the new Apple File system preclude that?
That will work if the USB flash is formatted on the older computer?
Another thought I just had:
Could I Airdrop files between computers?
Can files be accessed, in both directions, between two Macbooks, one running OS 26, and one running OS 10.11.6
