Typo in this page:
https://help.minecraft.net/hc/en-us/articles/360059148111-Minecraft-Java-Edition-Hotkeys
Item 16, third line:
16. Creative Mode:
X + 1-9 Number Key - Loads Toolbar Activator
C + 19 Number Key - Saves Toolbar Activator
I assume the command is supposed to read "C + 1-9 Number Key - Saves Toolbar Activator"
Confirmed. Thanks for the link and thorough description!