A friend of mine and I had a discussion why Browser add workspaces or side-panel like views inside them as I think the usage of multiple windows archives the same effect: separating a bunch of tabs.
They had the argument that it benefits as many windows get hard to handle when you try to find the right one in the taskbar after minimizing one.
So I had the idea "That's a good point. But why limit it to Browsers and Co and wait for them to implement such stuff (other example is tmux with terminals)".
So I started researching and found a Mastodon post (sorry, but I forgot where it was) that showed a Plasma shell inside a Wayland window.
With some tinkering I came up with this script.
Now to answer your question: it can help to organize a lot of windows, but each Plasma instance takes about 200 MB RAM and also on my computer the main Plasma instance kept crashing after some minutes.