So I have a folder Music synchronized with my Galaxy S23 and my windows server. I decided to sync it with my older Galaxy S10 phone as well (because it has an audio jack so it’s better for a car) On the windows server I just opened the folder properties and checked the checkbox to sync the folder with the S10 device. However nothing is happening and there is no message on the phone saying something about the new folder if I want to accept it! Weirdly the PC side says synchronizing but 0 speeds. Also weirdly the folder shows Actual on my S23 phone but on the server side it says unsynchronized in red letters! What and why is unsynchronized? When I put new folder there it successfully uploads to my S23 phone. Nothing happens on the S10 though…
OK so I found out that if I go to hamburger menu and tap “Syncthing GUI” there it is! A question “vitas-server wants to share this folder with you”. OK fine, but the problem is that I want to choose a location on my SD card, but there is no selection GUI! How the heck should I know how to type that path correctly in the Android SyncThing format? Fortunately I could go back from this and see how the folder DCIM is set and saw it is /storage/emulated/0 so I went back to Syncthing UI and the question was still there so I accepted the folder and typed /storage/emulated/0/Music and it works. Absolutely user unfriendly though :-\
Hi,
What is user unfriendly at getting an Android Notification “device … wants to share folder… accept?” and then the UI pops up where you could click the folder path field to select your preferred folder? Couldn’t be easier but always go better. 
It’s shown here how it works: (0:16:50)
OK I admit there was a notification, but I did not see it. I was looking somewhere in the app for it and there was just nothing! So the only way is to tap on the notification and then this accept folder dialog happens. Otherwise you can do it the more difficult way which I have described
Here are nice ideas on how we could improve: Review pending device/folder notifications "greyed out below existing entries" · Issue #742 · Catfriend1/syncthing-android · GitHub
from 4 years ago already 
4 years where I did not take the time to code a new UI. 