A very useful feature in KiCad is the ability to ‘edit | edit track & via properties’ to do a selective global edit. In that dialog there is the option to filter by net, netclass, layer…
A useful feature (in my opinion) would be to allow selection by a parameter such as width (for tracks) or diameter (for vias). Some PCB manufacturers will allow smaller vias (for example) than their “public” website specifies, but doing so incurs a price hike and longer delivery. Conversely, some manufacturers will offer a lower price for a less “tight” PCB (wider tracks & gaps, or larger drill sizes).
It would be great to select all tracks that are, eg, 0.21mm and change them to 0.20mm. Same deal with vias.
Would such a feature be of interest?