I am sorry to say, but there is no standard way to do so.
Windows are managed by your browser, so you can open it in a new window, but it is not part of the initial application if you do so. If you want to use windows you could open a new app in the new window. here is a post on how the communication between those apps can work: Communication between tabs or windows
Popovers allow you to access the rest of the app while they are open, but once you do the popover closes. There is a property, that stops it from closing, but this property also blocks the wished for interaction. (the property is named modal
check here: https://ui5.sap.com/#/api/sap.m.Popover/) Like every UI5 Element it can be made draggable, refer to https://ui5.sap.com/#/api/sap.ui.core.dnd.DragDropBase.
Dialogs do not allow any interaction with the rest of the app and i did not find a way to bypass it. Its has a build in feature for drag and drop though.
However
If you can do without the draggable part there is a way you can make it kind of work. It will only work as intended on desktops or large enough tablets.
You can use the FlexibleCollumnLayout
and open your content in a new column. That allows you to interact with the "Dialog" Content at the same time as the content of you main page. Like this the "Dialog" will always be to the side, so it is not draggable.
If you really want to have the draggable part you would have to create a custom control. Read up on the topic here: https://ui5.sap.com/#/topic/8dcab0011d274051808f959800cabf9f
I hope I could help you,
Eric