Microsoft is going to replace the Item Cross Reference functionality with item Reference.https://docs.microsoft.com/en-us/dynamics365-release-plan/2020wave2/smb/dynamics365-business-central/write-longer-item-references
Microsoft has created a migration feature for this
The breaking change consists of that it migrates from:
"Item Cross Reference"."Cross-Reference Type No." Code) --> "Item Reference"."Reference Type No." Code)
So it tries to migrate from code to code which means that customers that has for A LOT OF years been having codes > 20 characters now need to reorganize their data which seems like a very unnecessary action to me.
I have created an idea for this that aims to keep the length and increase the new field to 30 characters.
You can upvote it here:https://experience.dynamics.com/ideas/idea/?ideaid=de49b904-7334-eb11-8441-0003ff68e4a2