Unit hidden message - own ship yard

[JoeFour]

When I hover over my own Ship Yard token, I see messages like "5 unit(s) hidden". I realize units are hidden from the opponent, but when I click on the ship yard, I see no other way to do anything, and no information about what units are hidden there.

Any advice or guidance on what this means, and how to interact with my apparently huge fleet of hidden units, will be much appreciated

[TacticalSurrender]

That message is talking about your SY . You have 5 hidden. That note just tells you what you have hidden from your opponent, you can see them all.

[tarkalak]

When I hover over my own Ship Yard token, I see messages like "5 unit(s) hidden". I realize units are hidden from the opponent, but when I click on the ship yard, I see no other way to do anything, and no information about what units are hidden there.

Any advice or guidance on what this means, and how to interact with my apparently huge fleet of hidden units, will be much appreciated

A shipyard is a Ship just like other ships. On the back it has the generic hidden marker of your color. So your enemy doesn't know if that Group is Shipyards, Decoys, Scouts or Base or any other unit.