Heading styles currently require pressing 4 keys on an Azerty keyboard.

In order to get 

ctrl-alt-1

shortcut on an Azerty keyboard where 1 = shift-& you need to press 4 keys

ctrl-alt-shift-&

Please consider making this a user preference of add following alternatives

• ctrl-alt-& for  ctrl-alt-1
• ctrl-alt-é for ctrl-alt-2
• ctrl-alt-" for ctrl-alt-3
• ctrl-alt-' for ctrl-alt-4
• ctrl-alt-( for ctrl-alt-5
• ctrl-alt-§ for ctrl-alt-6
• ctrl-alt-à for ctrl-alt-0

see https://community.atlassian.com/t5/Confluence-questions/How-to-change-Confluence-Cloud-keyboard-shortcuts-for-Azerty/qaq-p/1631964?utm_source=atlcomm&utm_medium=email&utm_campaign=accept_as_solution_reminder&utm_content=topic

Could not find Confluence cloud as component so I selected Confluence Cloud Premium.