It may work copy the lightroom catalog to your internal drive, unplug Blue, and rename "Red" to be "Blue". (I assume the file/directory structure on your backup is the same as your original disk, or can be made to be the same.) How well this works depends on what else you've been using Red and Blue for, and (for all I know) what operating system you're on. However, I've done this successfully on OSX when all these disks are being used for is photo storage/backup. I actually do this regularly when my version of Blue needs to be replaced with a bigger Blue.
Alternatively, copy the missing files from Red to the right places (file/directory) in Blue. How to find the missing files? Do Library>Find All Missing Files (probably best done in Grid mode). How to turn this into a list of file names? There are a variety of methods described on https://community.adobe.com/t5/lightroom-classic/how-to-export-a-list-of-selected-file-names-to-share-with-a-collaborator-or-client/m-p/7346741 A little bit of light scripting can turn this list of files into a copy command from Red to Blue (I know this last point is one of those "less than a minute if you know the right stuff, and completely opaque if you're not a programmer" comments...)
You don't have to learn everything all at once.
Start with the simple stuff, master it, and then if there's something else that catches your eye, learn that.
To answer the original question:
You can make "droplets" in Adobe Photoshop out of any action. The droplets can be placed on your desktop and you can drag files (in bulk) to execute them.
If what you want to do is more conditional than a droplet, it turns out you can write Javascript to create Photoshop scripts (and lua to create Lightroom scripts). Though that requires a touch of programming skill
They might have an Epson printer, and want to avoid the update which makes the printer reject OEM (non-Epson) print cartridges.
I wish I'd known ahead of the "download new version" button.
I'm not opposed to this new "roll film" Mr. Eastman seems to be selling, but certainly, this new technology is going to invite laziness both in picture taking and post-processing. I mourn the loss of quality in going from reasonably sized glass plates to small film, and the lack of creator attention to detail that printing one's own pictures encourages. When prints are expensive, only the best pictures get printed to the actual print is a sign of intent and choice, encouraging inspection. With so many pictures being sent out for mass processing, I fear that roll film and Kodak processing will leave the world awash in casual and bad pictures, not to mention all the resources required to create so much film and paper, and the pollution that is sure to result from all that photographic processing.
Make sure you remove the white backing on the "scanner side" of the "door" (thing that swings up to make the glass visible.
Make sure your using the slide carrier (of course).
Make sure that you've got the "C" tab in the hole on the scanner frame. This will align the slides with the light source that has been revealed by removing the white backing (as someone has mentioned). I bet that's your problem.
Even if no one ever stole Adobe software, Adobe would have moved to the subscription model. The subscription model is stunningly more profitable; the stock market rewards subscription companies much more than ones that just sell things. If you want a more complete exposition of this point, try Scott Galloway's "Post Corona"
If the camera is compressing the images, then they take up less than the full amount of space you'd expect from the dimensions. Some images compress a lot more than others. Take a picture where most of the picture is blue sky, versus, say, a picture full of a lot of unpredictable detail, the first should be able to be compressed a lot more than the second---producing a smaller file size.
Amargosa Opera House and Hotel. It's a kick. In the park (or maybe just out of it). Expedia says it's $131/night, but it fills up quickly.
Scan your receipts. They take up a lot less space that way. Likely, they all fit on an SD card, but keep a backup in case you need warranty on that one.