Its likely to have been asked before, but...

When submitting a run, i noticed that characters had a "add value" box. Does this mean modded characters? And if so, where are they viewed?

Just an oversight on the settings end, it should be displayed as normal for you now.

Thanks for clearing that up. But on the subject of modded characters, perhaps a new category extensions board for these characters can be made at somepoint?

Whilst not on the table just yet don't let it stop you from running modded characters. The biggest issue you could imagine is you can see how cluttered our boards look right now with only 6 characters, but a whole host of modded characters would be quite the trek to get looking nice which is why we encourage it greatly in the discord but can't quite actively support it at the moment. Maybe if SRC introduces some new tools we could incorporate this change :)