Install in a subdirectory now, but move to main later

Yes.

From this: https://codex.www.ads-software.com/Giving_WordPress_Its_Own_Directory

Just set it up in the /meanwhile directory (though name it something else like … blog or wp or such) and then ‘move’ it.

I don′t know if it′s the same, this do exactly the oposite what I will. Here it′s installed in https://www.example.com first, and then moved to https://www.example.com/meanwhile. Are you sure it will be the same procedure?

I would like to install the wordpress site in a subdirectory, maybe https://www.example.com/meanwhile. When Im finished with my new site I would like it to have this address https://www.example.com
Is this possible?

Ipstenu gave you good advice but will reiterate:

To make WordPress available at https://mydomain.com in Settings->General, change the Blog address (URL) to https://mydomain.com and put this index.php file in your web-root folder (it is the same folder that contains the meanwhile folder)

<?php
/* Short and sweet */
define('WP_USE_THEMES', true);
require('./meanwhile/wp-blog-header.php');
?>

Then update your permalinks by visiting Administration > Settings > Permalinks and clicking on Save Changes.

Note: If you don’t like that approach, review Moving WordPress and Changing_The_Site_URL.

mettemor It won’t be the exact same, you’re right. You would skip the steps you don’t need to do ?? Those directions show you how to move from .com to .com/meanwhile and still have the blog show up in .com. You would skip the steps for the moving TO /meanwhile but follow most of the others.

Thank you both MichaelH and Ipstenu!