Is there a text editor that would allow me to create syntax highlighting easily?
Basically just the title said. The situation is basically I use a Domain-Specific Language called G'MIC, and to this day, I haven't found a satisfactory answer to the issue of lack of syntax highlighting. At the moment, I am using KDE Kate as it's pretty good at structuring the code with their find/replace feature, tab indicators, and multi-window support.
Take a look at Sublime Text. It has pretty solid syntax support plus all the other things you need (tabs, structure, tab ind, multi windows) and I'm pretty sure can pretty easily have a custom highlight config written easily if you're already comfortable with code.
I would use VIM, personally. It may take some getting used to, but once you get it, it can be very useful. (VIM does have syntax highlighting, by the way)
To make it clear, I have hard time getting “contexts” working.
Are there any particular problems?
However, if you're using Windows/have Wine installed and feel that contexts are an overkill, there is Notepad++' User Defined Languages, which as far as I can tell is purely based on lexemes.