Example, suppose during answering a question, external link of my answer is broken. So i removed phrase "Find more information about how to ask a good question here", until i find alternative link
If an answer is complete without a link, feel free to submit it that way. You can add a link like that later, once you find one, by editing.
From comments:
Sometimes it takes more than 3 hours to answer a post because of researching & reflecting on topic.
Yes, that can easily happen. Thank you for caring about post quality.
But if it's already taking you hours, then I don't understand why it's a problem to re-type a phrase like "Find more information about how to ask a good question here" once you find a suitable link.
If you find that a sufficient answer for a question doesn't flow naturally from start to finish (this may depend on the exact question), please copy out your existing text locally, and work on it locally. It's also possible to install local Markdown editors that have more functionality than the Stack Exchange submission form, if that interests you.
Stack Exchange and/or your browser may remember a draft of your post, especially if you just leave it open in a browser tab. But I wouldn't rely on this if you don't have to.
That said, it is possible to "save text for later" in a post, by putting it in an HTML comment. Keep in mind that the community can edit these comments, and that they are still subject to the code of conduct. Most editors would probably not remove an HTML comment like "TODO: add a link here once I find one that explains XYZ and is not broken" from an answer, but it's not reliable. On the other hand, maybe someone will find a link and edit it in for you.