labelWidget label; interactive widgets also use it for ID generation. A ## suffix can distinguish IDs without displaying the suffix.
p_visibleHeader visibility in Uint8Array[0]; write only 0 or 1. Its close button writes 0. Null omits the close button. Pass Uint8Array storage, not a JS scalar; native access uses the supplied backing memory.
flagsImGuiTreeNodeFlags options controlling this operation; combine compatible flag bits with |.
True if the header is open and its contents should be submitted. Unlike TreeNode(), this never requires TreePop().
Returns whether the header is open without indenting or pushing an ID; do not
call TreePop() for it.
When p_visible is a Uint8Array, its first element controls visibility. A
value of 1 displays the header and a close button; clicking the close
button writes 0 to p_visible[0]. A zero value hides the header.
Display a closable collapsing header.