Depends on how you want the info displayed.
I have / you could hack these core files to add your fields/replacing existing fields to the existing Web User Management :
manager/actions/web_user_management.static.php
manager/actions/mutate_web_user.dynamic.php
manager/processors/save_web_user.processor.php
Downside is no more easy upgrades, upside is seamless integration.
Equally you could use the example given as a starting point and create a Module or private pages etc.
I’ve attached a couple of screen grabs of method one.
If you just want to view them then maybe a module pulling through all the fields into a grid ?
I don’t know about the plugin idea, maybe someone else will chime in.
In the chunk I only have put [+bedrijfsnaam+] and [+kvknummer+] just to see if something will show up in the manager, is this this a good way to see if it is pulling the data from the modx_web_user_attributes_extended and show it in the manager?