I have made an app with some dashboards. Not everyone who uses this app needs all menus.
Is there a way I can set it up so a user could go to a configuration page and select specifically what menus to show?
Like a custom changeable navigation menu?
You can sort of do what you are suggesting but it will be set in place unless there is a way you can tweak your default.xml file to make it customisable for the user.
more info can be found here that should help you get started https://dev.splunk.com/enterprise/docs/developapps/addnavsplunkapp/
There is not any way i know off to do it directly via the gui