I was also looking up Pcb Editor / Edit / Edit Track & Via Properties… when eelik posted.
With that dialog you can filter by net, or by netclass or by layer.
Which prompts me to as:
Do you know how net classes work, and have you used them in your project?
If not, then learn about it. With a netclass, you make a set of rules (track with & clearance, via dimensions, etc) and then you apply those rules to a net, or to multiple nets. Once you’ve set up your nets in net classes properly, your modification is likely also easy.