I feel that I've seen a reference to this at least as an RFE but I am having trouble locating it.
Essentially, with the web client and ZD, if I "dismount" a share (my method is right-click/delete and empty trash), or simply refuse the invitation to access it, the share still exists for me to connect later if I remember the address. I do this by right-clicking on the word "folders" in the left pane, selecting "Link to Shared Folder" and then entering the email address and name of the share.
However I don't see a method, currently, for discovering shares in the web client and ZD. (IMAP/CalDAV clients and Outlook are another matter.) If one exists I'd appreciate a pointer; otherwise if there's an existing bug report/RFE I'd like to vote for it instead of creating a new one.