"Shan Ye Wan Li" can be used to describe the rolling mountains, and it can also be extended to a broad and boundless mind. In some contexts, it can be used as a confession to express the meaning of "you are my romance hidden between mountains and rivers". However, it may have different meanings in different contexts.
Secret love means that one party has love for the other, but it is not expressed. Therefore, if you use "Shan Ye Wan Li" to describe yourself as having a secret crush on someone, you can understand it as "Shan Ye Wan Li means having a secret crush".
In a word, the meaning of "Shan Ye and Wan Li" needs to be understood in a specific context.