FAB bar (i.e. floating action buttons bar) is the group of clickable buttons displayed on the left or right side of the screen. To edit FAB bars (or create a new one), go to WP admin -> Loyde -> Theme Options -> FAB (Floating Action Buttons) Bar. There it's possible to choose layout block displayed as FAB bar on the left- or right side of screen. To edit existing or create new layout blocks, go to WP admin -> Layout Blocks.
Its possible to build FAB bars using any page builder block. But for the theme demo, we've opted for the popup functionality, where a popup appears on hover i.e. tap.