"I offten do some coding in Vim and I miss an feature that will highlight
the word I`m writing in that moment and other same words. (It is mainly
for variables - sometimes I switched letters and afterwards I`m looking
for mistake for a quite long time. The NetBeans IDE has a feature like this.
I know about * but it`s for search in the text. I`m looking for something that work automaticly in insert mode."
You can use ctrl-o from inside of insert mode to enter a command, but to me typing ctrl-o * while I'm hammering out some code feels awfully cumbersome. There's also the negative side-effect that * jumps forward, so you'd lose cursor position, which would assuredly interrupt workflow. Instead, I'd just define a simple mapping along the lines of the following.
imap <F2> <Esc>#*A
So, you're inside insert mode, you just typed a word, and you want to match all occurrences. You would simply hit F2, and it would backward match the word nearest the cursor. This has the negative side effect of jumping backwards; thereby, losing cursor position. To compensate, we add a * to jump forward followed by "A" to return to insert mode and insure you're at the end of the line. Obviously, you can substitute any keybinding you want for F2.
This seems to work well on my machine; although, there might be more optimal solutions. If anybody has one, feel free to share.