I should probably have said patterns, not paradignms but this beside the point.
I mean stuff that is common enough to deserve a defintion and a best practice laid out in a human computer interface (HCI) guideline document for a platform/OS.
Off the top of my head:
Tab closing behaviour on Chrome/FF. Close a tab, other tabs shift but don't change size immediately so you the next tab's close button is directly under the mouse and can bel clicked to close another tab (and another, and ...).
Another one: the typical chat app with servers/groups/contacts on a list on the left and the chat on the right (and possibly threads on the far right).
There is no good standard for this, everyone cooks their own soup so stuff you learned for Slack doesn't apply in Discord etc. I.e. it's a pattern of some sort but there are no Windows/macOS/Qt/GTK interface guidelines covering this case and/or suggesting best practices.
This includes e.g. platform standard keybindings to select stuff in such apps (at best Tab switching works).
Another one is use of (some) Markdown-inspired stuff in chat apps. I.e. `monospaced` ```monospaced multline``` or even ``` ...```.
In Slack ``` works but ``` doesn not (but does in Discord, used to work in Slack in the past, I think).
I think there are many such patterns that are maybe not as groundbreaking than the invention of tabs (90's?), combo boxes/menus (also 90's? When there are too many choices for radio buttons) etc.
But beause they are used in some form (or another, unfortunately) by many apps now, the OS vendors should define a best practice for implementing their end-user facing functionality/behavior in their HCI guidelines.
Even if the platform itself doesn't provide a ready-made widget for each such case.
Hope that makes sense and explains what I meant.