Actually, the whole management of the nested part of the Instrument tracks inspector is broken, and the worse is that the key commands related to it also don’t work, from which, no workaround that I know of…
Even if it is related to pinning the available sections in it, see also this thread, which gives another view about the present Instrument tracks inspector state.
A true workflow killer that has been left as it is since I don’t know when, despite countless reports… 