They look like leafhoppers of some sort. I would just monitor the plants and wait for signs of damage before doing anything.

As far as I know they don't damage plants.

Yes, adult leafhoppers. A couple of dozen partially skeletonize a cluster of new blackberry leaves in my garden in early summer most years. The adults will not live much longer; the much paler, smaller nymphs should be watched more closely if leaf damage becomes obvious. You may not have any nymphs in your garden at this later date.

Leafhoppers do not have chewing mouthparts; they can't skeletonize leaves. Their damage is accomplished by piercing/sucking needle-like mouthparts, with which they siphon plant sap and spread plant diseases.

Signs of serious damage include stippling, wilting, plant decline.

That is true, but it is the only insect pest I have ever seen around the new caneberry growth.

Perhaps something is coming out at night to feed on your blackberries. Skeletonizing is the work of another pesky culprit.

Yes, the damage is consistent with tortrix or geometrids, but I have never seen those cats in the berry patch. Next year I will try to pin it down, it has always been too minor to investigate.