spidobot

Update:
 
I tried to deleting an old docker (gameserver, which isn't used, so if there goes anything wrong, it wouldn't be bad)
and setting up a new instance of it with the same configuration. (as suggested by squid and trurl)
-> all previous data (inside of /mnt/user/appdata/satisfactory/) on the array from the old instance got deleted. (just some test-gamesaves, so nothing bad)
 
so what did work for me?
0. stop "main"/"first" container
1. setting up a secondary instance with exact same configuration
1.a but with a twist: for a link to the filesystem, i just added a "2" (just so the name is different for the directory)
2. install
3. let container run for a bit to set itself up (optional, just wanted to be sure the container can install itself once)
4. stop secondary container
5. edit it's config to the "first" container (see 1.a: now all paths should be the same)
6. start up secondary container
7. check data/webui/gameserver/whateverYourContainerIs and delete "first" container
8. delete the directory from 1.a
 
this list could be shorter i know, but i was willing to do the extra steps, just to be rrreeeaaallllyyyy sure, since the initial test with the gameserver showed, that some docker installations overwrite the directory, if there already exists one.
 
same counts for dockers, which need a db-docker. on their first installation, they "migrate" (but simply overwrite and clear) an existing db.
happened with "wekan" for me. so above steps should also work for database connections, but i didn't test it.
 
maybe it helps somebody else.
 
thanks all for your time and inputs. they helped a lot!