The feature to add disconneted pages is nice, and very helpful for last minute ad-ons, but often I have wanted to "connect" these pages after creating them due to the flow issues that arise from adding disconnected pages.
What flow issues? The whole purpose of the disconnected page(s) is to add something outside of your current flow. If you want the contents
inside your current flow(s), then simply copy & paste and then delete
the disconnected page.
Otherwise, you can already connect the flows on the disconnected pages using the current tools. First find the location where you want to make the connection. Use the Format > Customize layout > Spilt Text Frame to break the current flow. Select the frame above the split and then the frame on the disconnected page and use Format > Customize Layout > Connect Text Frames to make the connection. Then select the newly connected frame on the disconnected page and the frame below the split on the original page and repeat the connection process. Your flows are now connected. HOWEVER, the content of the flows still resides on the same physical pages and your reader's won't know what exactly is happening here.
Perhaps a specific example might help explain what you exactly want to