Create own timeline

Good afternoon!

I need to make a user-friendly interface to create queues enemies.
The first thing that came to mind is the timeline, as in the animation. A timeline key would be responsible for the addition of a new enemy.

In fact, I know how to do enemies queue in the usual animation timeline. But it will not be easier than writing code that will add enemies in the script.

In the end, I need:
1.When you drag a prefab on the timeline, it creats key at the same time with the event, which would instantinate a prefab.
For each wave of the enemy, I need a separate layer (or simply line). Each should be edited in a mixed form - where all kinds of enemies are in one line and a separative form, where one kind of enemy has its own line. It is also necessary that for each wave summarizes the total cost of enemies.

Is it possible to do?
I didn’t found something about the timeline in manual
Maybe someone have to accept articles / links how should I work with timeline?

I want to know only if it possible to use standard timeline?
Or I should reinvent the wheel and make it myself?

Or should I write in Script forum section?