While Construct is quite a powerful tool, there's a few usability issues that make working harder than it should be. These issues are mainly in the Event Sheet Editor.
First of all, you can't create subgroups inside groups directly. If you want subgroups, you have to create a group outside groups and then drag it into another group. Not good.
Another things about groups: Please add a "New event" button to the end of each group! It's incredibly annoying to try create events into right places when at worst you'll have to make them to the end or start of code and then move into the right place or copypaste another event and change conditions. Right-clicking on an event and having a "Insert event" in the context menu wouldn't hurt either.
Copypasting actions is also working kinda funky: If you copypaste actions into a condition that already has multiple actions, the actions will be always placed after the first action, and not moved to the end of the actions.
Creating a new event by clicking on the left side of an event and then pressing the "new event" also tends to create the event somewhere where it clearly shouldn't be, like the start or end of the code, especially if you do this with an event that's located in a group.
One of the most important things: You can't press enter and have it register as "Finish" when creating actions! This is one of the most annoying things in the Event Sheet editor and slows down work a lot.
Power alone isn't enough if it's a pain in the ass to take use of it, so I'd say focusing on usability issues is quite important.