You shouldn’t need to add nets associations for traces in nets. Vias are able to implicitly use the name of the net they are connected to automatically.
The only place where it’s an issue is when using a via to stich pours together. Doing a “repour all” can cause some pours to back away unexpectedly because of an indeterminate net on the via during the pours.
If you need to, you can assign a net to multiple vias at the same time by setting your selection filter to only vias,
selecting a group of vias, and then hitting the inspect button on the right sidebar in the property inspector.