Hi @Anonymous,
I don't think this is available with the current OneNote create page action.
Currently it is only available to modify the page content, there is no available way to add the time string at the Title field.
For the time string, if you woud like to save the time into the format "dd/mm/yyyy - hh:mm", we could take use of Compose Action with the FormatDateTime action.
For example:

This would format the current time in the wanted format.
For the Google Calendar Start Event, change the formula as below:
"@formatDateTime(triggerBody()?['Start'],'dd/MM/yyyy - hh:mm')"
Regards,
Michael