Click the pencil icon to open the Page Editor.
Click the block settings cog.
Select Edit Collapsible Section Settings.
Select the desired Section Title Style from the dropdown menu.
Click Apply.
Choose a larger or smaller heading style for a collapsible section title.
Click the pencil icon to open the Page Editor.
Click the block settings cog.
Select Edit Collapsible Section Settings.
Select the desired Section Title Style from the dropdown menu.
Click Apply.