How to transfer only a subset of folders from an old imac to a new imac

Connect the two Macs together in Target Disk Mode  with the old Mac in TDM. The you can access the drive on the old Mac from you new one and copy the folders/files over as needed.

The normal and best way to transfer files from an old Mac to a new Mac is to use the Migration Assistant app provided by Apple for transferring your files. It is very easy to use. Then, if you have transferred some files you no longer want, you can simply delete them. Be sure to read and follow its instructions. Basically, the process is as follows.

You first begin by starting the process of setting up your new computer. You will be asked if you wish to transfer files. Respond YES and follow the instructions you will be given.

·      You will be told to turn both computers on and activate Migration Assistant in the old computer.

·      The computers should be connected with a USB cable to facilitate the transfer.  Wi-Fi is simply not suited for a transfer of so much data and corruption often results.  Do not use it. It can corrupt or lose data.

·      You will be given several options of what to transfer. You will likely want to transfer your settings and preferences.

·      You can transfer all or none of your files. You do not have an option to select certain files to transfer. If you wish to do that, then do so manually. You can transfer all or none of your installed apps. Some people elect to download fresh installations instead.

·      The old computer's operating system will not be transferred. No data from the old computer is erased.

·      Allow for up to an hour for the transfer process to complete once you start it.

·      It should set up the new computer the same as the old one.

Enjoy your new Mac.

I hope this is helpful. Good luck.

I don't understand what you mean by "a subset of folders". If you wish to only transfer certain items why not just copy them onto a flash drive and then copy from the flash drive to the new computer?