This is dependent on the trading platform. Personally, I use SierraChart, which exposes/uses an internal C/C++ "API" for end user programming.
In the case of SC, the WindowsOS API can be used to create dialogs (etc). So long as user created dialogs are NON-MODAL, there are no affects on the functionality of SC. How and when the interface element (dialog) is used, is limited only by the features and confines of the exposed SC API, and the users ability to write C/C++ code.
A generic possibility basically available to any user-programmable platform is to use a scripting language like Python or similar. The trading platform code could dump wanted information, perhaps through writes and updates to a file, and the script could read, process, and display the data OUTSIDE of the confines and control of the trading platform.