A more easy way to loop bars selection. Switching between instruments sounds.

Hi,
I'm pretty amazed by the app, it's wonderful!
I have a question. While working on the arrangements I often need to make a selection of bars to loop the song while playing with the chosen instrument to hear its sound. But if I'd like to make a loop on any other instrument staff I can't then select instrument I need to hear its sound. Another problem I often face is that it's pretty hard to make a selection of bars with the mouse if the arrangement is quite big, the mouse often points to the end of the bar making me zooming out and zooming in to the starting bar to try again. If there could be a keyboard way to switch between sounds of the instruments and to make bar selections by typing its values in a popup window it would completely fix such an inconvenience, thanks!