I was planning to create a bug report for that, but it's not a bug, so I think the right place is in the forum with mention to 
Ashley .
There are actually 2 little things that I would like to be tweaked in the UI of Construct 3.
1) The arrow to reveal a minimized action or group has a quite large hitbox on the right. Sometimes I just want to select a whole action, but end up maximizing it instead. I'd personnaly would like it to be 2 or 3 pixels smaller on the right.
2) The area where we can click to select the whole action (between the maximize/minimize arrow and the actual action) is not indicated when that action is not selected. So sometimes I end up selecting the condition instead of the whole action. It would be great to have even a nearly invisible vertical line as a separation at that point.
Both problems are actually linked. As the arrow hitbox is large, I know I have to click a bit more on the right and sometimes I mess up. Fixing one of the two problems may be enough.
On desktop build, the fact that the cursor is buggy close to the left part of an action in the event sheet doesn't help, too (that has been reported as a bug).