Plugin Name

Yes, we have made this compatible in a way that you can continue with it like before. Simple look for a new "Shortcode Factory" dedicated panel in any block's inspector sidebar. The panel hosts a button (Add Shortcode) which you can click to open shortcodes dialogue. The same you can achieve by clicking gear icon on default editor toolbar (a.k.a formatting/alignment toolbar).

Of course it is compatible with Classic, as well as, Gutenberg editor.

Yes, we are trying to gradually adopt new editor and it's features. We have already in plans to role out new changes and making it more compatible and native to the Gutenberg editor. Stay tuned for such changes in upcoming versions.

[scf-posts] offers filter_label_more filter, which can be used to override the default label for the link. See http://shortcodefactory.com/users-guide/scf-posts/ for details.

The "Register" link is not offered if the Administration > Settings > General > Membership: 'Anyone can register' box is not checked.

On WordPressMU, there is no /wp-register.php file, and /wp-login.php?action=register is not a valid registration form. Thus, wp_register function does not show a registration link.

Although, we have tested it in very much detail. But technically, it shouldn’t create a conflict, since it does not try to change anything in the Wordpress System.

[scf-allow] supports "short code within short code", so your other short codes in an [scf-allow]...[/scf-allow] block are rendered pretty fine.

Simply enable "Text Widget Support" option under Dashboard -> Shortcode Factory -> Settings and save changes. On the other hand you can add add_filter('widget_text', 'do_shortcode'); in your active theme's functions.php file.