Using multiple Apple IDs on Mac and iOS devices

I don't think you understood the question. Sorry, let me try to be clearer

I am logged in my Mac and All my other devices as USER-2

That account takes care of iCloud and email and enables syncing of Notes, Photos, etc.

For my iTunes and Media Purchases and Apps I use USER-1 which is my original AppleID - got this long before I started using iOS devices. I also use this for subscriptions and Family sharing

I have done this for well over 10 years on the Mac and my iOS devices

My problem arose after the last Mac OS update ( which may or may not be the problem)........ My media and purchases were also assigned to USER-2 as well as the device. So... I lost access to appleTV+, iTunes....ETC.

SO... I restored my MAC via Carbon Copy Cloner to my last backup 10 or so days. It was painfully slow, but I am back to my 2 ID System. I have made another CCC Bootable backup. Now I have to do a system update. Wish me luck

Don't ask me how I got it to work this way originally - I have no idea. I am planning to buy an M1 iMac soon but worried I cannot recreate my setup. Can Apple merge my 2 accounts?

Here is screen shots for Mac and iphone

If you want to use multiple Apple IDs on a Mac you probably need to set up separate user accounts. See: Set up users, guests, and groups on Mac - https://support.apple.com/guide/mac-help/set-up-other-users-mtusr001/mac

You can only use one Apple ID at a time on a mobile device such as an iPhone, etc.

Apple won't merge accounts. Read this to see what you can do:

Apr. 2018 post by ASC helper Winston Churchill on transferring data from one Apple ID to another. https://discussions.apple.com/message/33333380#message33333380

Feb. 2021 tips from Eric Root https://discussions.apple.com/thread/252468781?answerId=254653802022#254653802022

Look into using Family Sharing to continue to be able to use items purchased with one Apple ID with other Apple IDs.

Family Sharing - https://support.apple.com/HT201060

Set up Family Sharing - https://support.apple.com/HT201088

You can't merge Apple IDs.

Family Sharing will probably be the answer, but I am still curious how I was able to use the setup before with separate ID for purchases and subscriptions

Thanks

Sometimes different features have their own sign-in.