Ubuntu – Enter Unicode mathematical symbols conveniently

I want to conveniently enter Unicode symbols such as greek letters μ, ξ, … and mathematical symbols such as ∀, ∃, …

Using the character map is not convenient.

I would prefer to enter something like \delta and have it converted to δ by pressing TAB or any other key similar to many LaTeX editors.

The background is, that I want to use eclipse for editing Julia code. But being able to do this with the operating system is better than making eclipse do that.

Autokey-gtk seems to do what I want. But I cant get it to run. Crashes each time an event is triggered.