when I type data into a field on one tab, it appears to be duplicated in another tab
Probably you have selected both tables.
Add a field next to a dynamic hyperlink to another range. The formula will show if the data is duplicated. Explain what a “dynamic hyperlink” is?
Try this.
duplicate-by-hyperlink.ods (10.0 KB)
The symbol » in column A indicates the presence of a duplicate. Clicking the hyperlink allows you to find the first occurrence of a duplicate in another sheet range.
You must understand the solution, otherwise it will be difficult to adapt it to your data.
NOTE: Named ranges are used, between which a hierarchical dependency is established. Range1ThisName and Range2ThisName are relative (current row value in column B).