Is there a way to specify search and replace range using the current line as a reference? I can specify range using explicit line numbers like
:5,15s/foo/bar/g
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:help :range gives you all the details; you can do quite sophisticated things, e.g. :'a;/pat1/-1.
For ranges starting from the current line, a neat trick is to start command-line mode by prefixing the : with a count: E.g. 5: turns into :.,.+4.
Protip: Learn how to look up commands and navigate the built-in :help; it is comprehensive and offers many tips. You won't learn Vim as fast as other editors, but if you commit to continuous learning, it'll prove a very powerful and efficient editor.
You can use . for the current position, and .+10 for 10 lines down:
:.,.+10s/foo/bar/g
Some other useful ranges:
% for the whole file.'<,'> for the lines of visually selected block. This might get you more than you want of the visual selection starts or ends in the middle of a line. The whole line is included.'a,'b from mark a to mark b..,$ from the current line to the end of the file.