There was a way to import from even wordpress for example and phpbb, so inputting collections should be 'easy enough'. Yet I haven't found a way to do it, but your wants will prompt me to look again. Not that I have much inclination, time or hope.

Whilst nosing around I found a relevant file or two, so will have a look for and at them and update their locations.

UPDATE:

/inc/tools/model/

contains files relating to Wordpress and phpbb and there's an 'abstractimport.class'

Edit. 2
I have three or more installs, each with multiple collections :(

Edit 3
Have you seen
https://b2evolution.net/man/?s=import&submit=Search&disp=search

@amoun Thanks for your having an eye on this forum and your willingness to provide support with your knowledge and experience.
The reason why I have to act is, my b2e versions run with PHP 7.3. And one hoster told me, the he will end offering this version. Now I have the choice between upgrading to at least PHP 8.1 - for which support will soon be discontinued - i.e. actually to PHP 8.3, or paying a disproportionately high amount for Extended PHP support. This pushes me.

Because my b2e Version 6.11.7 is also rather old and I noticed some security risks which could not be fixed for this version, I think about closing this Instance with four collections.

So I've started archiving the pages of the collections that are more important to me on archive.org, so at least they won't get lost.
In 40 days I will upgrade to PHP 8.3, just to see how it breaks my version of b2e.

I will keep my second instance for the time being, as this hoster will continue to offer PHP 7.3 for the time being.

I could try upgrading my instances to the latest version of b2e, but the last time I tried this I failed miserably.

Again; thanks a lot and I hope I'll meet you here again in case of other asks for support.

Best wishes and keep up your great work
Will

I had problems with 7.2.5 and php > 7.4.# :(
I had to backtrack from 8.1
I may try again.

You may be better off running your own server with php 7.4 and installing b2evo there.

I use a raspberry pi with apache 2.4
The Pi can be as cheap as £45

You can install a server on any computer, and using LAMP to install with php and Maria Database.

Here's my server, I chose not to use a domain name as my broadband provider gives a static IP address.

Here's the server/host front page
http://217.155.51.23

and here's an example of b2evo 7.2.5
http://217.155.51.23/unveiled/raspi/server/