There's no way to do that as far as I'm aware. I've always interpreted 'Include' as a way to override an exclusion when multiple condition tags are applied to topics.
Rh2020 is a bit more TOC based that Classic, in that if a topic is not in the TOC and isn't linked to by any topics in the TOC, then it won't be included in the output. However, any linked topics will be pulled in. If your project doesn't include a lot of links between topics, perhaps this method could work for you.
The most reliable way of excluding content has always been by using condition tags and excluding specific ones.
You can bulk apply condition tags using the Topic List report. There are some filters you can apply to narrow down the results and show and hide different columns. You can also sort on columns. Tick the checkboxes for the topics you want, right-click and select Properties, then you can select a condition tag to apply to all the selected topics at once.