Is there something like Vision Client Tags in Perspective?

[Felipe_CRM]

From a quick search it seems that pageIDs stay active until the session associated with that tab times out.

Check if a pageID is actually active

No, there's a timeout. Browsers are not required to notify a server of tab closures, and generally don't. I think you are going to have missed notifications if you have to target only one page.

EDIT: the timeout duration is 60 seconds to be exact, at least as of late 2022:

Pages still shown in pageIds key after being closed

Just a note here: closing a page in your browser (or through a script) essentially closes the websocket for that page. On the backend, this registers as a connection loss, and we give the page 60 seconds (by default) to reconnect. During that 60 seconds, the page will still show as part of the session. After the 60 seconds have elapsed, we remove the page from the listings.

See also the following: the pageID is associated with the tab, not a view, which sounds like a good thing in your case.

Dynamically Change/Animate Docked View Handle Icon

What you're hitting here is an unfortunate terminology issue which I see all of the time and which I FULLY understand. the onPageStartup script fires one time when you open Perspective Page in a tab. It does NOT fire every time you perform page navigation. Watch the pageId during the life of your session; the pageId does not change as you navigate between pages because what's really going on is we're just swapping out the View on the back-end and applying any rules from the Page Configuration. …