Hi @Si Hobbs ,
According to my research and testing, you can create Reusable Content in SharePoint.
Create Reusable Content:
1.Go to Site content >> Reusable Content List.
2.Choice Reusable HTML.
3.Enter all the column values and save the list item.
Use Reusable Content:
1.Go to target Page >> Edit Page.
2.Click on Page Content field.
3.Click Insert>> Reusable Content
4.Select the reusable content that you want to add and it will be inserted in the field.
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