Now that I see the full thing written out, I feel like it should be なくさないよう（に）注意してください 
If you’re copying a sentence someone has written, I’d copy the full sentence as is, without adding or removing kanji and say where it came from (and any additional relevant context also helps)…you’d be amazed at the confusing sentences that come up, only for someone to randomly come along and say “oh yeah, I’ve read that…this happens on the page before so it means this” 
Unfortunately there’s nothing native…
<ruby>感じ<rt>ふりがな</rt></ruby>
will do the job though, and if you don’t mind userscripts, there’s one kicking about that does it more automatically.
Also this page is useful for learning all the clever formatting tricks: