Having to reselect "highlight" tool each and every time

I am having trouble with my highlight tool on my laptop where every time I make a highlighted mark, I have to move the cursor back to the toolbox to reselect the tool, make the mark, move the cursor back, reselect, make the mark, move the cursor back, and so on... I am needing help to find a way where I can select highlight (or any other comment tool) and it will remain selected for as long as I am marking the text. As a PhD student who does a lot of reading and a lot of marking of that literature, having to go back and forth each time I select a line to highlight becomes much too time consuming. Please help. The function I am looking for exists on my desktop, so I know it is possible, but I never made any changes to make it that one. The Acrobat Reader comment tool functions just turned to different defaults on my respective computers.