To have a matching behavior for both VSCode and Compass apps use a single CertKey file picker on the connect form instead of having two separate fields for certificate and key. The `sslCert` and `sslKey` node driver options accept the same file type and `sslCert` can be used to accept a single file that contains both certificate and key.

https://mongodb.github.io/node-mongodb-native/3.6/api/MongoClient.html#.connect

The old documentation always sets both the cert and key, but they do the same thing. 
It is all linked to cert and key here https://nodejs.org/api/tls.html#tls_tls_connect_options_callback which supports "certificate chaining".
 
Note SSL options are deprecated but still supported. If specified both TLS and SSL options the TLS will override the SSL options because they are just aliases.