Impossible to transfer files from iCloud desktop to external drive.

Re: "Keynote is containing an overly huge amount of storage in 'Applications'

Do you have any idea why that application would be so huge - and where I can delete the files if it is embedding them in itself. (Perhaps that's why my Systems Data appears so huge too?)"

There may be many temporary files created as part of that regular workflow, or if you create updated / improved versions, saving them all as you go. Else full-resolution images used in creating presentations .... animations .... do use up space.' If you use quality audio ... that may also use a lot of storage-space

If you have copies of everything valuable:

You may consider deleting and re-installing Keynote if there's nothing there you'll need.

More info: Delete a Keynote presentation on Mac - Apple Support

or

Uninstall apps on your Mac - Apple Support

Thank you for your reply, and added info. Commiserations on your situation!

Re: "The point is that my Mac computer used to work fine but it suddenly developed all kinds of quirks when Apple started updating the O/S. (I have auto updates on.)"

From your screenshots, seems there is an update available for download, and your Mac is seriously short on memory / storage space. (Recent MacOS updates may include Apple intelligence which requires memory / storage space to install.)

Screenshot: The Mac OS version shown is 15.1.1 . There have been 5 updates available since then. What's new in the updates for macOS Sequoia - Apple Support

Eg: A Mac generally needs at least 50 Gb free in which to operate smoothly, and to do all you ask and expect it to do. As well, it needs enough space to accomodate any updates, and update process. Video work is memory-intensive.

Apple support provides guidance on how to:

Optimize storage space on your Mac - Apple Support

___________________________________________________________________

Re: heaven knows what 'System Data' is (348.79 GB), or where it's located?

Find and delete files on your Mac - Apple Support

Eg: says:

• "System Data: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files and other runtime system resources. Also included are temporary files, fonts, app support files and plug-ins. You can’t manage the contents of this category. The contents are managed by macOS and the category varies in size depending on the current state of your Mac. You can manage your data that falls outside the other categories using the Finder or the third-party apps that created it."

Eg: Any temporary files from memory-intensive video work may be stored in system data, and may be managed by clearing work-files from the app that created them.

_______________________________________________________________________

Re: "my desktop files are permanently embedded in iCloud now, so I cannot easily open or export them!"

iCloud use generally requires up-to-date software.

Have you tried opening the files on iCloud.com (Your screenshot says you have 111.5 Mb stored in iCloud Drive, which is only a tiny amount of files).

Files in iCloud can be accessed on the web using any trusted device:

ie: Sign in and use iCloud.com - Apple Support

iCloud: https://www.icloud.com/

iCloud Drive: https://www.icloud.com/iclouddrive

You can: Check your iCloud storage on any device - Apple Support

Am no expert ... the way I understand it ... Apart from any back-ups you may make, iCloud is mainly a sync. service that keeps all files you choose to sync. accessible across trusted devices to ensure you can access them on any device.

Files in sync. stored in iCloud should be openable on Mac or on any other devices listed in your Apple Account, (for large files .. if space permits).

Time Machine is a good way to keep everything on your Mac stored externally.

or

You can save anything on Mac via drag and drop to an external storage drive.

You are in charge of what you choose to store / sync using iCloud:

Change which apps sync and store data with iCloud - Apple Support

Manage iCloud storage on Mac - Apple Support

___________________________________________________________________

Re: I don't install any software that is not from a recognized provider either -

not anything.

Great! Apps like virus-checkers, ad-blockers, cleaners and the like, even Chrome and VPN are known to cause interference or other issues.

Any necessary third-party (non-Apple) apps need to be kept up-to-date, so they remain compatible with MacOS.

Re: " ... transfer files from iCloud desktop to external drive."

Wondering which iMac model you use, and whether your iMac is using an up-to-date or earlier MacOs version:

Seems ICloud is secure storage, as needed in today's climate where data protection and privacy are important.

Apple Support has an article online that may help:

See how to: Archive or make copies of the information you store in iCloud - Apple Support

Apple's tips for using external storage drives include ensuring the external drive is using an approved format:

Connect and use other storage devices with Mac - Apple Support

File system formats available in Disk Utility on Mac - Apple Support

If needed: how to: Erase and reformat a storage device in Disk Utility on Mac - Apple Support

If needed: iCloud Support Website: iCloud - Official Apple Support

Re: " ... I don't get 'Recommendations"

Strange. I see them there on my (older version) of MacOS.

See if you can change those settings: Change Storage settings on Mac - Apple Support

Re: "I can't backup my large files to an external storage device before deleting them to free up space!"

In Storage window: You can try clicking the (i) button beside the various categories, and you should see the files listed, so you can see what is taking up the most space in each category.

Else if you have enough external storage space, you should be able to back up everything you wish, just by dragging files, and or folders to the external drive, or by backing up your Mac using Time machine.

Connect and use other storage devices with Mac - Apple Support

Thank you for your replies, and for sharing your plan!

A few thoughts:

✽ You may also need to delete files associated with keynote.app

You can enter the file extension .key in the search bar in a Finder window.

You will likely see a list of files that were created.

Click on a file to highlight it, and it's location appears in the status bar below

✽ Temporary files can be removed at any time by restarting a Mac:

Eg: Click the black Apple on the left in top menu >

click "Restart" in the Apple menu that opens

✽ Remember to empty the bin to re-gain the space from deleted files.

You may need to Restart the Mac to see the decrease in Storage.

✽ You will most likely need to re-install Keynote from the App Store.

(Keynote is an optional app, not one of Apple's regular apps MacOS updates.)

Eg: If needed: see: "How to redownload apps on Mac" in the article below

Redownload apps and games from Apple - Apple Support

All the best :-)