I have used Family Tree Maker which syncs to Ancestry. You download the trees to FTM and merge them, and then upload to a new tree. The merging is tedious but better than “save to tree” bit by bit. It is the ONLY method I found that preserves the records as records so that all the connections between facts and the records are kept. Going through gedcom is a waste. I have had cases where people trying to find birth parents would build a separate tree for each DNA match. That can be extremely time consuming, to impossible to combine into one tree. But often the only way forward.
For about 100 people I helped with finding birth parents (I take that to mean building the complete and verified 5 generation tree for them) the best and most workable method I found was to add each DNA match to the tree, mark them with a DNA symbol using the Media Gallery to add the people to a small number of symbols, link the DNA match page to the person in the tree. It seems like a lot of work, but it is routine and what you end up with is a tree that encourages all the related trees to grow and quickly find connections. If you don’t know how a person is related, you can just add them to the tree, mark them with a symbol so you can find them in the tree, and then link their DNA to themselves in your tree. I normally build complete pedigrees for matches that don’t connect. It helps them and their DNA matches, and eventually the branches begin to overlap. Keep an eye on duplicates and learn how to merge duplicates (start with the good one is best).
Also learn “edit relationships” so you can disconnect and reconnect people if they are in the wrong relationships. Then you can concentrate on adding records and tree connections (I usually link ALL related trees) quickly and efficiently, knowing that you can change the tree if needed. When you are trying to build a tree from DNA alone, there might be many wrong places you try – just so it is easier to see the relationships. You can build islands of connected people, then arbitrarily connect to that island by putting placeholder people connecting you to their common ancestors. Then make sure in the Tree Settings that you are the person who is the home person in the tree. That lets Ancestry compute the relationships.
You use the computed relationship in the tree for each DNA match and the DNA genetic distance to see if you have the right approximate distances. That (being able to check many different DNA matches distances quickly is also why you just routinely add EVERY DNA match to your tree and keep track of them. Often just pure persistence and method will solve these cases. I have done it alone about a hundred times, and worked with others as well. Just getting all the matches into ONE tree is the most effective tool. I have many many many suggestions for improving Ancestry, but they have their own interests. They make more money when it takes people longer. They don’t seem to realize that 7.8 Billion people is a lot more than they serve now.
Many people don’t know how to merge trees or how to copy them (without loss). I think that many software packages can sync with Ancestry and other sites now. But what is really needed is a complete and lossless exchange format that can be used globally.
Glad it was helpful. It took me several years and many tens of cases before I realized how essential it is to help ALL the DNA matches with their trees. If you do not, even where there are many good trees and genealogists in the matches, the whole will never come together on its own.
For those people in parts of the human species where there are not so many genealogists or records, it takes that much effort (building ALL the trees of all the close and many distant DNA matches to a high quality) to have enough organized information to solve a missing parent case. I think the computer could do about 95% of the work.
I feel bad that I am getting too old and tired to do it anymore. And all that I found will just disappear. I guess that is life, but it doesn’t seem fair somehow. There are about 2% adopted, NPEs and missing parents in the world. But sadder is that of the many tens of millions of people who have taken DNA tests, about 99% of them do not have a complete pedigree. I could image a nonprofit group that would do it. In my early days, even though I was raised Christian, I respected the LDS for their goal of building a global family tree. I guess they just gave up one day. They had their reasons for wanting everyone to know their ancestry in detail and correct. But I see how it weakens societies when they do not feel connected.