Two of the pieces of information entered onto the current request form are the Year and the Change Request Number. These are currently manually entered (i.e. type into the field 2018, and type into the next field 1, 2, 3, ....(whatever the next sequential number will be)) into the infopath form.
When reviewing the process on Friday, my manager has asked whether this could be made automated (i.e. when you click on 'Create a new item' it will automatically pre-fill the next number: 2018-001, 2018-002, 2018-003, ...).
Whilst searching online I can find plenty of ways that seem to do this using older versions of SharePoint (2007, 2010, 2013) and SharePoint Designer, I haven't been able to find out how to do this using SharePoint online and Microsoft Flow.
The pre-filled field should look like YYYY-###, i.e. 2018-001 for the first request raised, 2018-002 for the second request raised, and so forth.
We can't use the ID number, as this doesn't correspond with the request numbers (as the ID number won't is already above 1, due to test entries from when I was building the system and checking that it works.
Also, there are multiple lists in the workflow, so the ID numbers in the different lists won't match either (due to testing, some requests stopping at the first stage, etc.).
Is there a way to have when a new item is created on the list, for the field to look at the previous item on the list, and add one to it?
Replacing the ['ID'] in the expression you have given with something that will give the next number?