Hi Florian, What db do you use? I use Legacy Premium so I'm not sure if all the features I use is available on the free version. FTM is similar.
legacy has a built in app that you log into your FST with, chose an ID of the person you want, choose the number of ascendants and/or descendants. And WAIT.
Then you work on merging the FS info into the your db. Since my target ancestor was Thomas jester
https://www.wikitree.com/wiki/Jester-129 At FST he is
https://www.familysearch.org/tree/person/details/LQRS-RW5 The LQRS-RW5 will appear in the index of Legacy once I've completed that. Legacy will have two red arrows, and as I sync up the data between the two the arrows turn green, when I'm finished syncing and click the "done sharing" button. If I change my db info or FST, the buttons will turn one green and 1 red.
On Legacy premium version, I can go into edit and add WT-ID to a user id box at the bottom, and there is a FAG id box also. Then in the index, I can make those boxes appear in the index. I have them next to the RIN (legacy id number). I can't sort by the custom numbers, but at least I can see what I've done and what i'm missing. I've used premium for so long I'm not sure what is on the free and what is on the premium.
I also have FTM tht I save for my cousins' ancestry trees.
3 cousins from different branches have given me their log ins at ancestry so I can 1. fix their trees, and 2. do additional research not available on FS.
FTM will also allow you to download from FST, but I haven't used that feature there yet.
But I did find something interesting with FTM. DO NOT download from ancestry as a gedcom. You can do a tree transfer. when you download as a gedcom, it strips out the REAL source link and puts in this code that is a broken link. something like amdredir. I've got about 15 files from one cousin's tree where I was working on his duplicates and other tree errors.
I know anyone who has cleaned up an ancestry import has seen the broken source links. Thats what causes it. I found out when I decided to do a gedcom import into instead of a direct transfer.
I haven't tried FTM on FST yet so I don't know how it handles the data.
WT also has a FST sync, but it adds the bulleted source without a link or other pertinate data. And its only viable on profilles you manage, and does not import persons.
Then once I have my db and WT synced by hand, mind you, I go to the FST profile, Other info, Custom Fact and add the WT ID and link.
I'm really not much for "leaf chasing" but I like FS hints better then ancestry's. So I can copy the source links directly into WT. AND, since FST is also a collaborative tree, I can fix the errors there too.
I've been using Legacy since 1990s. My brother does not do genealogy, but works with it to study family patterns in social networking. Ph.D in anthropology. He uses the free version. It does everything he needs it to do. A friend of his got a grant and bought a high dollar program, we're talking several $100s, And Legacy does everything that high dollar program does. Even the paid version is significantly cheaper.
Legacy will also sync with MyHeritage if you use that. I don't, because like ancestry, its full of junk trees.
Yep, I turned this into an ad for legacy. sorry.