Your TS has some errors (ul not closing and one bracket missing for NO state).
Just set the active class with the ACT menu state, which is for the menustate of menuitems at rootlevel.
lib.menu = HMENU lib.menu{ 1 = TMENU 1.noBlur = 1 1.wrap = <ul>|</ul> 1.NO { allWrap.insertData = 1 allWrap = <li id="nav{field:title}">|</li> } 1.ACT=1 1.ACT{ allWrap.insertData = 1 allWrap = <li class="active" id="nav{field:title}">|</li> } }
Reference for item states.