UKC

how do i add boulder problem, for example doing a stand start for a sit start ? This would not be a first ascent but a problem stand start  Nearcliff Wood

A stand start to a sit problem isn't a new problem. You're working the problem. You can add sitters to stands but not the other way around.

Just type in the original name of the problem when adding a new climb ie. Lesson in Depth and put "Stand" at the end to get "Lesson in Depth Stand" 

If you scroll to the bottom of the listed routes/problems theres a link to "add missing climb" then follow the prompts and add the info. 

Theres quite a few like that already at the crag you linked.