Anyway, I'll let it go, and just roll my eyes at all the hacks and duplication that building an entirely Ajax UI using pure JSON responses entails.
How about SolrInfoMBeanHandler.java adds a simple "searchHandler" attribute with true/false?
I think it would be just as easy and far more generally useful add a request param to SolrInfoMBeanHandler that would let you filter the objects by what class's they are an instance of just like it can filter by "cat" and "key" right now (ie: "/admin/mbeans?class=solr.SearchHandler").
As far as this issue in general: i think it's a good idea to add a pulldown to make it more friendly to folks and easier to use in the common case, and populating the pulldown with all the instances of SerachHandler makes a lot of sense, but we should try to use some UI element that will allows people to type in their own handler name if they want (ie: http://jsfiddle.net/6QeXU/3/ but i'm sure thers a clearner more efficient way to do it) so we don't anoy people who have their own custom RequestHandlers that don't subclass SerachHandler, or want to use things like MoreLikeThisHandler, etc...)
(Longer term, it would be to make querying the AdminHandler return all sorts of useful introspection info about what is currently running to drive the UI screen generation, with optional config on the handler to override things maybe i don't wnat to advertise some search handler instance?) along the lines of this brainstorming doc i write a long, long time ago: http://wiki.apache.org/solr/MakeSolrMoreSelfService#Request_Handler_Param_Docs)