This answer relates to the portion of the question dealing with fringe indicators. When the fringe(s) are visible, they appear to the immediate left/right of the window body. The manual contains a diagram explaining the terminology:
https://www.gnu.org/software/emacs/manual/html_node/elisp/Basic-Windows.html
The fringe-indicator-alist
is a buffer-local variable which may be customized to include various fringe indicators. To inspect the value of this variable, visit the buffer at issue and type C-h v
aka M-x describe-variable
. The default value in Emacs 29 is as follows:
((truncation left-arrow right-arrow)
(continuation left-curly-arrow right-curly-arrow)
(overlay-arrow . right-triangle)
(up . up-arrow)
(down . down-arrow)
(top top-left-angle top-right-angle)
(bottom bottom-left-angle bottom-right-angle top-right-angle top-left-angle)
(top-bottom left-bracket right-bracket top-right-angle top-left-angle)
(empty-line . empty-line)
(unknown . question-mark))