widgets – Implementing a sidebar with foldable boot cards

I'm trying to implement foldable boot maps (Bootstrap 4) on the widgets of the sidebar, until now I have this:

register_sidebar (
board (
& # 39; name & # 39; => esc_html __ ("New Sidebar", & nbsp;),
& # 39; id & # 39; => & # 39; new_sidebar & # 39;
& # 39; description & # 39; => esc_html __ ("New Sidebar", & nbsp;),
& # 39; before_widget & # 39; => & # 39;
& # 39 ;, & # 39; after_widget & # 39; => & # 39;

& # 39 ;, & # 39; before_title & # 39; => & # 39;
& # 39 ;, & # 39; after_title & # 39; => & # 39;
& # 39 ;, ) )

The problem is that each compressible container needs a unique identifier to find out which one is open or closed, but my problem is in "before_title". and & # 39; after_title & # 39; because I am not able to replace it with an identifier. Can someone help me? I'm still pretty new to WordPress.