You can use the Patch function in Power Apps to create a SharePoint list item.
This is quite easy and documented on the Patch function page.
But what do you do if you now want to get the details of the item that you just created.
Today I discovered that the Patch function returns the item created. So that means that I can set a variable.
This variable can then be used to get the ID of the list item.
You could now for example use this item id to update another datasource with the ID in SharePoint.