I am facing the same issue. I have a dependant dropdown that filters out invalid combinations, however the user is given the option to "SHOW ALL" which renders my dependancy moot.
I need to be able to find a way to remove that option so users cannot select an invalid drop-down. The only workaround I have now is create a check for each invalid combination and create a validitity check module. This is a lot of maintaince when simple removing "SHOW ALL" would solve the issue,
Currently there is no way to Disable Show All button as per my last discussion with Anaplan Product team although they mentioned that it is one of the backlog items for them to look into for future release.
Honestly. Well over a year now and this should be an easy fix for their development team. Would've loved to hear the final approval discussion for this "feature" when they were originally designing it!
I am facing the same problem here. I have trouble understanding why when selecting to restrict access by using the "Selective Access" option we would have the "show all" option which cancel the very functionality we are trying to implement. Would be great to be able disable that "show all" option.
Feature of disabling the "Show All" option in selective access or dependent dropdowns is planned to be released today (9th Dec 2017). After this release you should be able to disable the "Show All" option. Screen shot of the same is available in this post.