I think you might have missed the last part of the tutorial which shows how to add Asterix in form of the sign “*” to display multiple items of e.g. a muscle.
Id you click one muscle e.g.
and display its activity
Then replace names with * like this
it will display multiple muscles… it is not all of them since they are placed in different folder levels.
you will also need
Back to your questions:
1: No, this is unfortunately not directly possible from the GUI, it is possible but only through writing some extract small script which picks out e.g. element 50 from the muscle name list and display its name. The 61 displayed on rectus muscle has nothing to do with the 61 in the plot, this is a coincidence, the 61 in the rectus muscle is there because the study has 61 steps, which means all output variables will have this dimension, so if you click any muscle you will see 61.
2: all muscle activations are numerically represented, if a muscle activation is 1 it means it is 100% active and it is working at its limit, many muscles will have activations around zero with a very low number( i am not sure i understood this question)