memory managment and (its) protection under Linux

partially OT : programming task
Scenario : Debian Bookworm, XFCE4
Very often GUI programs show their results in the form of ListBoxes, whose content is mainly textual semantically, but very often cannot be copied/pasted as text and neither is easy to export as text. I have one case in FreeFileSync, that shows lists of files upwards of 500'000 items, and other deduplicators programs.
I am having a general curiosity about this problem in linux.
Can a root user access, in read only mode, to memory associated to another (plain user mode) process ? Or the outcome is invariably a seg_fault ? Has a root user the right to inquire the memory of non root programs ? I am not speaking about disk files, but specifically in physical memory
Those gui programs must be storing long list of strings in memory somewhere.
The first question is : is it there any way to escalate read-only access to memory assigned to other programs ?
If the answer is, YES, then the problems evolves to
is it there a way to query the system (X server ? Who else ?) what is the topmost (active desktop, foreground) graphical element at given mouse coordinates ? Are list boxes standard enough to be accessed in a fairly portable way disregarding the many different graphic engines (QT, GTK or else) and DM (I have XFCE, but there are plenty of), so to locate the strings arrays ? I can guess many frameworks could implement internally listboxes in different ways and debugging would be hard ! But the first thing to be clarified is : I need some handle to memory allocated to it in read only mode. Only then I could think to attemptively elucidate the internal structure of the object. I am assuming to not have any source code of the program or of the underlying framwork.
If I had the code itself, it would be much simpler to extend it, obviously, and to add a menu item with an ExportList cmq.
Tnx for any suggestion about the memory management and protection under linux kernel.
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MarioCPPP