layout_block_configure_form in core/modules/layout/layout.admin.inc

Form callback; Add or edit a block within a layout.

layout_flexible_template_configure_form in core/modules/layout/layout.flexible.inc

Form to manage adding and removing rows to a flexible template.

layout_flexible_template_edit_row_form in core/modules/layout/layout.flexible.inc

Form to add or edit a row on a flexible template.

layout_flexible_template_region_style_select in core/modules/layout/layout.flexible.inc

Form to select the region widths for a flexible template.

layout_menu_item_form in core/modules/layout/layout.admin.inc

Form callback; Configure a layout menu item.

layout_settings_form in core/modules/layout/layout.admin.inc

Render the settings form for layout.