Pleas insert Mod Support, it same of Steam, Thank you.
If it´s not possible with a workshop, you allow to use Mods to install with a Mod folder and activate in the Settings of the Game.
Thank you.

I agree. It's frustrating that only the Steam version can activate mods, even though the tutorials show you how to put it in a local mods folder before uploading to the Workshop.

was looking at buying Project Highrise Architect Edition for $12.00. Is there still no mod support in the GOG port?

You guessed it, nope. Searching led me to this post. And no one seems to care. They should support nexusmod (developers should).

Edit: No mod should be hidden behind a seller's infrastructure. I am reluctant to buy any future games from someone who does this. Very disappointed with developer.

Yeah, I'm similarly angry about this;
I did see some really good mods in the steam workshop and wish I could use them with the gog version....