How can I merge Notes from two Macbooks without using iCloud? I have two laptops and both have different Notes that are useful to me.

Not wanting to share any such data with Apple, they are also not synced to iCloud.

So far, I found the path where they are stored:

~/Library/Group Containers/group.com.apple.notes


And see that the "DB" behind this is sqlite.

Is there any way to export all all the content in one directory and then clear all notes so the files can be re-imported?

I could see perhaps altering a bit the sqlite DB (or merge the two) and then have my notes from both Macs in one place in the end but lack a starting point or guide. I know iCloud sync is the easy way, but consider confidential data from clients where we agreed not to store the data online or transfer / store it external to the Mac in question.
You can use Exporter (free app from app store) to save all notes as text to a folder on your computer. Then import them into other notes. 

It likely did work equivalent or extending on this reverse-engineering effort to get data from the database that backs the application:


https://articles.forensicfocus.com/2013/11/02/analysis-of-ios-notes-app/
What format does the apple notes sqlite db date use?


You could also just set up an IMAP server (even on your Mac) to sync up and then merge down the notes. iCloud isn’t the only server that can sync notes.


Sync Notes from Mac and iOS devices without iCloud