So I can verify that Mike's answer worked. This is really useful to me--thank you.The clarity about a short answer and a long answer important. Here are the actual steps I used to verify the short answer which Mike provides. I am running 14.1.
• Open Wolfram and set up a notebook the way you want including overriding existing styles and adding new styles.
• Export a stylesheet using Format->Edit Stylesheet Export button.
• Call it StylesheetAlpha.nb
• Close Wolfram and then reopen it
• Open a new notebook called Work.nb
• Open StylesheetAlpha.nb
• In Work.nb, use the commands below to define variables myNB and myStyleNB. This eliminates any file commands other than opening the two notebooks. You have to scroll in the list provided by PopupMenu to get the right notebooks.
• PopupMenu[Dynamic@myNB, Notebooks[]]
• PopupMenu[Dynamic@myStyleNB, Notebooks[]]
• SetOptions[myNB, StyleDefinitions -> NotebookGet@myStyleNB]
• Save Work.nb
• Close Wolfram
• Delete StylesheetAlpha.nb and empty the trash to make sure it isn't being used. And that everyting is truly embedded.
• Open Wolfram
• Open Work.nb
• Check to see if the styles work as expected. Look at them using Format->Edit Stylesheet.
It all worked! And it only has to be done once. From then on Work.nb has the styles in it.
Mike, wonder if you would share your source for learning about this? Was it just the online documentation or is there a tutorial you found useful.