You will probably get this warning because the duplicate individual that was on both GenoMap using hyperlink with be removed (the hyperlink will be remove since they are now on the same GenoMap).
After paste, delete on of 2 duplicated invidual and re-link the tree part with "Link as Child" or "Link as Parent".
If you use Cut and Paste, all your hyperlinks will disappear .. this is a huge pain if you have to reconnect multiple people.
I suggest the following:
1. Go to the genomap you want to copy from.2. Hit CTRL+A to select all, then right-click and select "Move to Genomap"3. Select the destination genomap, and place the tree where you want it. All your hyperlinks will still be visible.4. Position the 2 hyperlinks close together, and then delete one of them ... the appropriate Parent or Child link will automatically form.5. Find the next pair of hyperlinks and repeat step 4 until finished.