Has anyone (and can tell me how to) or is it possible to create an additional user “customer” for example and open up webfig pages with only certain variables available?
For example a router is deployed but a customer wants to manage his own wireless password, can there be a webfig page with ONLY wireless password available for editing?
Yes, design a skin for the user. Create a new end-user security group, assign that skin you have designed to that end-user security group, assign a new customer username and password to that security group - you can even test the look and feel without having to constantly keep logging in and out to see what effect you are having, the design skin feature allows you to switch views.
We did this in our WISP a long time ago. Our customer gets a RouterBoard but they can only log in and see a limited cut down view of the router config. Plus they can only break unimportant things, such as their wireless SSID and password 
See https://wiki.mikrotik.com/wiki/Manual:Webfig#Skins for more info.
Fantastic! Thank you.