I am playing with a design where the top side of a 4-layer PCB would directly act as the "user interface": No components, no traces, just black soldermask and white silkscreen. Capacitive touch sensors for user input will be placed on the upper inner layer, and output will be via a small display mounted on the PCB bottom, behind a milled cutout. All active components are SMD parts on the bottom, of course.
Ideally I would also want to avoid visible via holes on the top layer, to keep it as visually clean as possible. The low-cost manufacturers don't offer blind vias, but plugged or epoxy-filled vias would be an option.
I can't have Ground on the top layer, for cosmetic reasons and because it would increase stray capacitance of the touch sensors. The top layer would be just soldermask over bare FR4. So, in order to avoid little humps at each plugged via location, I want the vias to have no annular ring on the top layer.
Kicad offers that option in the properties of each individual via: Annular Ring can be set to "Connected layers only". But how do I set it for all the vias? Is there a way to make it the default property? (Can't find this in the board setup dialog.) Or can I change it globally via the Edit > Edit Track and Via Properties dialog somehow? (I can't see that particular setting in the global Edit dialog.)
Thanks for any pointers you might have!