What you are looking for is called a modeless (or non-modal) dialog box.
You have to create a dialog box template for those like for normal (modal) dialog boxes. But instead of using
DoModal()
you have to use
Create()
and
ShowWindow()
.
There are also more things to observe with modeless dialogs; especially where the instance is stored and usually to avoid multiple instances to be created.
A rather old but still valid link:
Tutorial - Modeless Dialogs with MFC[
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