The display of stacked images you mentioned in the LR desktop app is not supported by the web app, or mobile apps at this time. It is on the team's roadmap, but I can't say when this will be implemented.
What I can recommend is to hide images from the view of others by setting the flag "Rejected" on your HDR bracket (source) images. When images inside a shared album are "Rejected" you can still see them as the album owner, but other people visiting your album will not see rejected images at all. I understand this may not be ideal for you depending on your culling workflows. It's the one workaround currently available to you at this time.