I tried to flesh out your idea a little bit below.
I don't have a Mac, but I think the basics of right-click and active-Window are similar enough.
Let me know, if I got anything wrong.
FWIW, I think the idea is very interesting. But I've never seen something like that at least on the Windows-side.
The only thing that kinda works like that (not activating a window you do stuff to) is drag&drop.
Is there any Mac-software that has a similar feature?
I do understand the need to want to elimante any unnecessary action.
I recommend to go to Preferences>Keybindings and setting up "Thought Icon>Paste Icon".
If you're using Firefox or something Chrome-based, there are extensions that'll allow you to copy anything you see directly to the clipboard.
Something like Vimium.
Whatever you're trying to do, there's no good reason, that you'd need to bother with the mouse, if you know what you're doing.
And once both hands never leave the keyboard, you'll be doing things faster than you can imagine.
Pretty sure, he's talking about active and inactive Windows. The active Window being the only one that excepts keyboard-input.
And there being only one active Window at a time. (pretty sure that's true for Mac and Windows)
And doing stuff in a TheBrain-window without activating it (because since you'd immediately want to go back to your browser, that's an inconvenience).
On Windows 10, something like that is already possible to a limited degree with drag&drop.
In Windows 10 you can drag and drop the icon from the url-bar in the web browser straight into TheBrain
This will make the URL the child Thought of the active Thought, without activating TheBrain-window.
So you can immediately hit ctrl+t or alt+d to continue surfing the web, without needing to worry about alt+tabbing first or clicking the browser-window.
He'd want to extend that kind of functionality a little bit. Instead of dragging and dropping, he'd just have an image or an url in the clipboard.
Then he'd want to be able to right-click on a Brain-Window and have a paste-menu appear:
that paste-menu offers him when right-clicking empty space on the Plex:
"Paste as an Icon for currently active Thought",
"Paste as Plex Wallpaper",
"Paste as Child Thought of active Thought",
"Paste as Attachment to active Thought"
that paste-menu would offer him when right-clicking a specificThought:
"Paste as an Icon for THIS Thought",
"Paste as Child Thought of THIS Thought",
"Paste as Attachment to THIS Thought"
And this should be doable without TheBrain ever becoming the active window.
This wouldn't be confusing, since if people want to activate a window, they'd always left+click it normally,
not right+click it.
This having to switch back to the Browser doesn't seem like a big deal, but if you have a large batch-job,
each step you have to do, adds a lot more strain, requires more focus and will eventually lead to you making frustrating mistakes.
Imagine you have a Plex which shows you all 150 Pokemon as names, each Pokemon has an individual Thought.
But the Thought is only text and that just isn't good enough. So you want each of the 150 Thoughts to have an individual icon.
Icons for each are easy to come by, you just have to google them.
If you add 150 alt+tabs to the mix, that'll make the process a lot harder, less fun and error-prone.
If you also have multiple Browser windows open, you might also have to make sure you're tabbing back to the correct window.
This is an extreme example, but a lot of jobs are like this sometimes.
Icons are nice, but there's a lot of Thoughts in your Brain, so each step of friction that can be avoided,
will make actually prettifying your Brain with icons a lot more usable.