How do I combina AND-blocks and OR-blocks?

I know how to make several AND events, and how to make OR-blocks. But is there a way to make both in the same without creating sub-events?

Like for example:

If (Touch AND Overlapping) OR Keydown

There probably is, but I would be inclined not to. If you have complex logic then it can be better handled by being broken up using subevents, or using local variables to store interim values, or using Families to group sprites together (for example). Clarity and readability are usually more important than brevity.

You can use variables

I guess subevents would be the best solution then? The solution with variables might get a bit messy in larger projects.

It really depends on individual cases. Pick whatever makes your code clearest - sometimes this is variables, sometimes it is expressions, sometimes it is events.

Use object families.