Roboko

In Invision Community, you can use either your name or email to log in by default. Invision Community does not have the concept of Username and Display name - There is just simply 'Name'. 
However, in my community accounts are created from a game where people have Display Names (Not unique) and Usernames (Unique). 
Ideally I'd like to use the Display name as the 'Name' that shows up above people's profiles and can be searched on, mentioned etc, but still have the user log in with their username. Something like this possible? 

When entering your key, did you add -TESTINSTALL at the end of the license number?
See the following for details:
 

you should add  -TESTINSTALL at the end of license key !

Here's an example of adding JS and CSS into a project: 
 
You'd do the same thing, assigning the JS template you've created to the relevant page. 
The next step is to adjust your Database template so that it applies that new JS. In the case of IPS, they added it in a <section> tag using the data-contoller attribute.
<section class="ipsType_richText ipsType_normal" data-controller='core.front.core.lightboxedImages,guides.menu'>  

This database includes TOC as well 
You can install it and just apply JS and CSS to your database.  
Here is an example https://invisionify.com/fxdocs_demo/introduction/create-toc-on-the-fly-r2/

Yes, that's possible: Invision do it on their Help Guides section, which is built with Pages:

They do so using JavaScript, and then mark then place an anchor and title like this in the page:
<a id="generalterms" rel=""></a> <h2 class="cDocs_mainTitle" data-role="title"> General Terms </h2> The script then looks for anything marked 'data-role="title"', and uses the relevant text to generate the menu, creating links to the preceding <a> tags.

Hi @Roboko
Here's an example you can plug into a custom php block for testing purposes. Just update communityUrl, apiKey, and the specified member ID:
<?php //REST API URL and KEY $communityUrl = 'https://www.yourdomain.com/'; $apiKey = 'abcdefghijklmnopqrstuvwxyz123456'; $id = 1; //Member ID // REST Endpoint $endpoint = "/core/members/{$id}"; $curl = curl_init( $communityUrl . 'api' . $endpoint ); // POST data $curl_post_data = array( 'customFields' => array( '3' => 'foo', '4' => 'bar' ), ); // Prepare data for cURL POST $curl_post_data = urldecode(http_build_query($curl_post_data)); //Turn parameter array into a string that looks like 'category=1&author=1&title=test file', etc. Only non-null items are included in this list. urldecode turns characters like %26 back into &. // POST Data curl_setopt_array( $curl, array( CURLOPT_RETURNTRANSFER => TRUE, CURLOPT_HTTPAUTH => CURLAUTH_BASIC, CURLOPT_USERPWD => "{$apiKey}:", CURLOPT_POST => TRUE, CURLOPT_POSTFIELDS => $curl_post_data ) ); // Get Response JSON $response = curl_exec( $curl ); // Build object $response = json_decode($response); echo \IPS\Member::load($response->id)->url()->setQueryString( 'tab', 'field_core_pfield_3' ); echo \IPS\Member::load($response->id)->url()->setQueryString( 'tab', 'field_core_pfield_4' ); Hope it helps!