I did something like this. It's kind of boju meets second brain. My life is extremely project heavy.

My work project box looks and works pretty much like the original image.

My personal cards are vertical. It's a trade off.

Pros to vertical:

They work well with a "Field Notes" notebook as a place to capture an index/ goals/do last/ want to research lists, etc as a traditional, if tiny, boju.

The vertical 3x5 cards fit in a clear pocket protector as a mode of transportation, (although I often just clip the day's cards to the front of the field notes notebook). The whole works fits into a cargo pocket in my slacks.

Vertical cards lay out nicely on my desk as a task list with the top line of each project card showing.

Cons: not a lot of pre-made resources exist for a vertical system. I've adapted.

I mostly use sticky tabs instead of pre-made dividers. Otherwise, my task/project cards are pretty much set up like Memidex/ Side Track Home Executives/ 43 Folders. I'm using a tall 4x6 card storage (Globe-Weis) box and have two rows of 3x5 cards side by side.

I've seen complicated ways that people index their knowledge cards. Zettelkasten, for example. I just use the Dewey Decimal System. I'm a librarian and professor, so I already know the Dewey System, but I can always quickly check to see where a subject should be filed by looking up a book on that topic in any library catalog. I just note at the bottom of the card if there are any connected notes filed elsewhere. I put book knowledge cards for fiction in 801 by author both read and to read.

I note in my bujo index where any card is filed (knowledge or project), and if it has a status. Task cards are rarely indexed and are often written on scrap paper that is trimmed 3x5. It works. I am not researching the same information repeatedly, stuff gets done, and I have an archive of completed projects.

My calendar is required to be digital at work, so that never figured into my system. If I have a busy day though, I write it out on a card with appointments and times in red and other reminders in pencil.

This system has saved my sanity. I literally had so many to-do list items and projects that no digital system could really handle it. And probably some undiagnosed ADHD, so getting away from checking things on a screen has been a game-changer. :-)