How do I copy data from one Quicken Mac to a new Mac computer (has new Q downloaded) ?

Open Quicken on the iMac then choose menu File > Show "filename" in Finder. When the finder window opens, you will be pointed at username > Library > Application Support > Quicken > Documents > QuickenFileName. Right click on the quicken file and choose Compress File. Copy the resulting zip file to a flash drive or cloud site to move it over to the other computer. Then double click to unzip it.

If you like, you can go up two levels and compress the entire "Quicken" folder in Application Support and move that to the same place on the other computer. To directly open the Library folder, hold down the Option key in the Finder while clicking the Go menu, then choose Library.

Note: the file compression step is important so that file/folder permissions are coded properly. Do not just copy the file itself.