The new Atlassian App Migration Platform (currently under development) will enable all Atlassian Marketplace Partners apps to build automated migration paths for their apps.
When a customer migrates from Confluence Server / Data Center to Confluence Cloud using the Cloud Migration Assistant, the app migration platform will coordinate with SVG Out to automatically transfer the app data.
Currently SVG Out macros can't be migrated automatically. The main reason is that some required parameters have different names and that the Cloud version uses attachment-Ids to reference the SVG to show while the Server / Data Center version uses attachment name and page name.
We are currently evaluating the best solution to allow an automatic migration of the majority of all cases.
Users have to re-embed all SVG Out macros. Open the macro editor, select the appropriate SVG, select width and height etc.