anchored split screen across desktops Is there a way to have split screen, where one side remains anchored across all spaces/desktops?

What I'm trying to do is essentially have two desktops split on the same screen, much like if you were having two screens connected at the same time side by side.

Currently the only solution seems to be split screens but on different desktops (i.e. if swipe to another desktop, new split screen setups, not one persistent one), but I want to have random things like spotify, chats, etc. on one side whilst I flick between apps like browsers, word, programming software etc.

I have a widescreen so I have the space to do that, frankly otherwise this screen I just bought is too wide!

FYI I'm using the LG 34" 5k2k widescreen 34WK95U
I've come up with one approach for the LG 34" 5k2k screen...

On the same mac, I connected with a thunderbolt 3 cable, and then via an adaptor I connected the same mac via HDMI, the solution being the mac thinks you're connecting to two screens, and the LG monitor thinks it's receiving two input signals which can then be displayed via PBP mode.

I have a 75/25 split and I'd say the resolution on the 25 side needs to be modified so text is readable which for me is at 800x1350, which doesn't give much space but just about works... I wish it supported 70/30 and it'd probably be better.

If someone has a single-cable split screen solution for what I describe, I'd love to hear it!