In BotW, they had the Ancient Saddle which basically worked just like that - whistle, and your horse teleports to you from wherever you left it, even if it was the opposite side of the map. The downside: it was DLC content, ugly, and didn’t work everywhere (the Taobab Grasslands for example were randomly off limits despite not being dangerous for horses).

That item was not even included in TotK and since they said they don’t plan to make DLC for the sequel, I don’t think we get something like it. Unless they decide to add it in a patch or update or whatever. TotK definitely needs something like that to make horses more useful.