Not sure if I understand your question fully, but you seem not to want to use UC Surface on a computer or tablet to transfer a project/scene to another mixer. I had a look how my Win 10 Laptop stores project/scenes and also checked the manual. It says in the
"UC_Surface_ReferenceManual_EN_04042019" (section 7.1.1 Import/Export): "You can copy individual Projects to and from your mixer’s memory by simply dragging dropping them between the Mixer and Local sections of the Library Management area."
Obviously the "Library Management area" is the computer and the path is (in Win 10) Documents > PreSonus > StudioLive AI > Library > Presets > Project. In this Project folder I see the individual project folders (suffix ".proj") and inside them at least two files: "01.name scene.scn" and "name.cnfg". Therefore I think I could just copy a single project folder with the two files in it on any medium (stick, card, harddisc) and copy this folder to another computer (with UC Surface installed) in its "Project" folder. I suppose, if I launch UC Surface then, my project will appear in the "local" list so that I can copy it to the mixer and use it there.
I made a screenshot of the project page of UC Surface and the Windows folder. The three projects stored in UC Surface under "local" show up as three indivdual folders with the scene and configuration files inside.
Hope this helps.