Regeneration order to “Ascending” instead of “Descending”

There is not currently a way to change the processing order.

It appears that this is being handled by JavaScript code here – https://github.com/Automattic/regenerate-thumbnails/blob/master/src/routes/subpages/HomeRegenerateMultiple.vue#L103

You could work around this by creating a fork of the plugin and changing the JavaScript code. Feel free to submit a Pull Request if you would like. To accept it, we would want to make this a configurable setting somehow, or perhaps controlled by a WP filter.

Alternatively, feel free to submit an enhancement request to the Github repository.