It's under the + icon (the same icon that you use for adding a game), and it's the Import Archive File option. I'm not sure what you mean by "splited", but it worked for me when I used it for the zip of version 1.0.1 of Para Ark 2.
Ah, I see. The zip file that I successfully had Joiplay unzip for me was the itch.io download, where I imagine you didn't have to do the split. Maybe for Patreon you would be better off just including a link to Mega or somewhere for the download, which I think is what most devs on Patreon do.
