>> so gltLabel4 corresponds to "#10 Session_Anxiety"?
Since you created this label "Session_Anxiety" in one of those glt specifications, only you can answer this question.
>> since both Anxiety at T1 and T2 are under the heading of "Anxiety", how do I enter the mean anxiety for T1 and T2 separately in 3dLME?
Remove the center (e.g., mean) of "Anxiety" for T1 and T2 separately outside of 3dLME using whatever program you like (e.g., R, Python, Excel, Matlab), and then feed those numbers back into the table in 3dLME.
Gang