How to add a scroll bar to a series of nested cards?

[Ildar_Gabdullin]

@Dretherix

and I’m trying to add a scroll bar to a bunch of cards I’ve stacked on top of each other on the left side of the sidebar layout

In your code only the 1st & 3rd card have “position: sidebar” set, not that huge vertical-stack.
So, it is unclear what “stacked” cards you wish to scroll.

@Dretherix

      - type: custom:card-mod
        style:
          ha-card:
            max-height: 80vh;
            overflow-y: auto;
            scrollbar-width: none;
        card:

This is a wrong card-mod code, should be like

      - type: custom:mod-card
        card_mod:
          style:
            xxx {
              ...
            }
        card:

If you choose a “scrollable sidebar” way - suggest to ask in card-mod-theme thread. Solution was posted here.