Sometimes I’m missing certain special character in VIM/VI.

A short google search will probably provide the correct code to enter those, but there’s also a built-in way: digraph.

As soon as you enter the command :digraphs in VIM, you’ll get a table of all available special characters and the code for how to enter it.

Remember that code (like two symbols), return to the edit and press <ctrl>k + the two symbols in insert mode.

<ctrl>k + <symbol>

As usual, the help will also provide some useful information as well as symbols.

:help digraph-table