Links to additional pages from "profile"

Here are some links that should assist, it explains how to add new HTML fields and tabs to a detail page:
https://wpgeodirectory.com/docs/core-place-settings/
https://wpgeodirectory.com/docs/core-place-settings/#fieldset
https://wpgeodirectory.com/docs/core-place-settings/#html

On the detail page, you linked, the menu in the side are essentially the normal tab links but customized with special coding.

Let me know if I misunderstood.
Thanks

1) I saw that the profile page (usually referred to as the “detailed listing”) can have a link to the external address, e.g., to the user’s website. This is fine (BTW, can I make it “nofollow” for free listings?).
That is possible with some additional custom coding, but it may not be a good idea: https://wpgeodirectory.com/support/topic/make-listing-weblink-nofollow-free-follow-paid/
A better option may be not to allow website links for free listings.

2) Another option is to offer users an internal link which, although is “internal” for the website, it is totally “outside” of the GD. The content of such a page will not be “known” or “controlled” by the GD. As far as I understand, such an option is possible and allowed, right?
You can allow any type of link to be added to a listing, for example to a facebook page, website, internal page of a website, etc.

3) Moreover, I saw that the profile can have a link to “photos” which will access one or more images. These images can be uploaded by users, and will be saved in the GD’s database (ready for import/export). I like this idea very much, but I want to know if instead of photos it can be html/text/etc.?
The link to photos is a link to a bookmark on the same page.
You can add heaps of different custom fields to a listing: HTML, text etc
See more about custom fields that can be added: https://wpgeodirectory.com/docs/core-place-settings/#custom

4) So, my main question is: Can I insert into the profile a link(s) to a *secondary page(s)*, and allow users to upload html/text/etc. for this “secondary page(s)” through the GD?
No, but you can add a link to a detail page that goes to another tab on the page that allows whatever you like. Just like the link to photos, and the link to maps, etc. You can add as many tabs as you like (which you are calling links to a secondary page), but they will all be on the same page.
If you really want separate pages for the same user, then you can use linking between different custom post types or the franchise addon.

Franchises allow sub-listings:
example: https://wpgeo.directory/docs/places/united-states/new-jersey/toms-river/transport/classic-cars/#gd_tab_franchises
info: https://wpgeodirectory.com/docs/franchise-manager-add-on/

Custom post types, allow linking etc:
example of a linked place [morimoto restaurant] to a place [music hall]: https://wpgeo.directory/docs/venues/united-states/minnesota/minneapolis/concert-halls/music-hall-minneapolis/#link_business
info: https://wpgeodirectory.com/docs/linking-custom-post-types/

5) Suppose, this link will be called “my biography”?
a. Can the text on this “my biography” page become part of the GD, be saved by the GD’s user, be imported and exported by the GD?
Export and import can be done by admin for any type of listing and fields, see https://wpgeodirectory.com/docs/core-export/

b. If yes, can I create such an option for the users by using the GD’s editor, or only by adding some code manually?
An Add Listing page is automatically created when setting up GD, extra custom fields etc.

Let me know if I still misunderstood.
I suggest you set up a site and get started, it will all become clearer, and then we can give more practical pointers.

You may also be interested in our UsersWP plugin, which is specifically for user profiles, whereas GD is for any type of listing: https://userswp.io/

Thanks.

You’re welcome 🙂
Just start a new topic if there is any other help you need.