I’m currently working on the SynoCommunity package to get integrated with the DSM user interface for “Certificate Management”. It no longer works for DSM 7.0 however, because Synology decided to limit the API to only their own packages. See the PR at framework, syncthing: Implement DSM managed certificate for services (fixes #3436) by acolomb · Pull Request #4930 · SynoCommunity/spksrc · GitHub.
So for DSM 7 you currently only have the option to copy the certificates manually. I’ve posted a script to do that in another topic because the old one was locked.
Sorry for not replying sooner, I seem to have missed a lot of notifications from Discourse lately.