At the time of writing, I'm using Garuda linux version KDE dragonized non gaming.
I have a external hard drive connected to my system. I want to encrypt a single folder present in that drive .
I repeat , a single folder of that drive , not the whole drive.
So How do I do that. Please, I need it urgently
That's not related to Garuda Linux.
Please search the web.
It sounds like an xyproblem. Remove your threats.
As @librewish has already stated for you, KDE has this feature already built in, and as @petsam has already stated our users are expected to do research on general type questions on their own.
This question has probably been asked thousands of times over the years and asking it once more only proves you have limited initiative or search skills.
If you insist on asking for advice on a topic covered many times before, at least show that you have done some of your own research. Otherwise it simply comes off as you are too lazy to do your own research. It goes like this, search the terms:
"encryption choices Linux"
Then if you still can't decide after doing your own research you formulate a question in this way.
"I have searched the internet for the best choices for encrypting a single directory. Many of the relevant posts I've found are older and the information now seems outdated. The most likely choices I've turned up are, Encryption A, Encryption B, and Encryption C (Vaults) . Of the 3 choices " Vaults" seems like the one that I find most the most applicable choice. What are users experiences using Vaults? Is it a good choice for encrypting single directories in your opinion" If you don't like Vaults, what others do you recommend? "
If you want to post a question that has been posted a thousand times online before, at least show you've done some research yourself on the issue, and you won't be told to "learn to search". Show some initiative and you'll get far better results on our forum. The lazy tend to get short shrift here.
If you wish to find further in depth tips on how to search and find the information you need, refer to my article on the Wiki:
The solution has been marked.