https://forum.paradoxplaza.com/forum/developer-diary/modding-development-diary-1-guest-entry-paradox-mods-in-cities-skylines-ii.1626999/
Of course, the in-game interface is not the only way to manage your mods: Playsets can be constructed from the Paradox Mods website as well. There, mods can be added, removed and toggled - and all of this will then be synced to your game automatically. Likewise, playsets are stored in our backend and will be replicated to all devices you happen to play the game on. And consequently: No, your carefully constructed playsets will not disappear if your computer lets out the magic smoke inside.
Mods discussions are also available directly from in-game - but the same discussions are also present on our forums, if you would rather post from a web interface. You can also find links to other (SoMe) platforms related to the mod, if pointed out by the creator.
Naturally, there are other ways to get mods than from Paradox Mods; creating them yourself for instance. Of course, the game will allow you to add local mods of any source to your playsets - Be aware that these will not be cloud-synced and will indeed be lost on catastrophic system failure.