This could be in main categories or category extensions.

How about a category called half% where you only play 18 out of the 36 levels (so beating 3-6) Just an idea.

Sounds like the prequels category that already exist. https://www.speedrun.com/lswtcs?h=Prequels-PC-Solo&x=n2y7zw82-kn0j047l.810e0joq-6nj4v7jn.jqzke28q

i think this could open up many different routing possibilities in order to complete 36 levels. like is it faster to beat up to 5-3, or up to 3-3?

Oh, any 18 levels. I see

Alternative idea:

Tyler%

I believe the route for that would just be prequels

What about an Original Trilogy Run?

That is already a category

OT category has been discussed and the rules are always too arbitrary to add. And for an 18/36 level category, OT levels are too long to be worth it, it would just be prequels