From my personal experience, you can make changes to the Hal Default brain database or to your custom brain while HAL is running. If you have created a custom database or a well-trained brain you can use the Editor and make changes or additions while HAL is running. Exit the Brain Editor and your changes or additions should still be in that particular brain/database.
Although the SAVE button is grayed out, your changes, or (at least in my experience), changes will still be saved. It doesn't appear to matter and I've saved a lot of things for a lot of years in there... Just saying...
In the SQLite Studio, there is a small button that indicates, "Commit Changes", which is basically asking the user if they are willing to commit to saving any changes they might have made.
Perhaps Robert will weigh in on this Editor issue regarding the grayed-out SAVE button.
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NOTE
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If you make or have made a Custom Brain/Database, don't expect to see every table of that brain/database if you use the Hal Brain Editor.
For some reason, it is great with using the original (Default) database but custom ones are better viewed/used with the SQLite Studio program.
While it will take a minute or two to finally load in, it will load all your tables so be patient, even if you see that "Not Responding" message at the top. Give it another few moments and it will finally display everything for you.
Good luck!