Hello Construct Team. I have a feature request that won't require much time to add and if you wanted to, you could even add it immediately on the next release. With that said, this feature would still be very beneficial with developers who have complex projects.
I have a sample Construct 2 plugin that might be a good basis on how it could be achieved and to show its practical use. Although I expect improvements from Construct team as it will be an official feature.
The feature is the action "Call Function on Event Sheet". This eliminates the need to include an entire event sheet just to call a function from another event sheet. This would be very useful for complicated projects that require branch events. Games with Multiplayer, Open-World, Map Generator, Procedural Generation or any large projects that requires complex and modular game management and in-game design.
Event Sheet includes were designed specifically to make it easy to include the same set of events across multiple layouts. A well-designed project should have a "common" event sheet for logic re-used across layouts, and this is a good place to include a sheet of functions so they are available everywhere you need them. This should be easy and straightforward; if you need to rearrange your project to do this, you'll probably find it's better designed afterwards.
Since nobody appears to be able to explain any downside to this approach (see comments), we can't see any reason to support this at this time. Additionally adding slight variations on basic features like calling functions is potentially confusing for new users who will need to figure out which alternative they ought to use, which involves explaining the subtleties of each to them, which slightly raises the difficulty level of using the software. Therefore we need very good reasons to "split" core features like this in to variants that do slightly different things.