(Since I host with Discourse itself, plugins are a non-starter.)
The next best thing, that I can think of, would be to ask…
Can a Theme Component provide a new sort-method? Sort by date of scheduled topic timer iff it’s a timer to publish to a category. And it would have to display the topic timer information in the Topic list. And it would have to visually distinguish topics that don’t have a topic timer (since the point of a category displayed this way it to be garden for cultivating topics that all eventually get published.)