Mostly!

On Windows, your profile folder data, which is most of what you care about, is stored here:

C:\Users\<username>\AppData\Roaming\Mozilla\Firefox

Note that AppData is a hidden folder. You can set Windows to show hidden files and folders: https://support.microsoft.com/en-us/windows/show-hidden-files-0320fe58-0117-fd59-6851-9b7f9840fdb2

I suggest making a backup copy of that entire Firefox folder including all of its files and subfolders.

IMPORTANT: Firefox uses the "Roaming" path for the important data. You can back up the "Local" path but it doesn't have your bookmarks, logins, etc., just temporary files.

One way to remove profile data -- after you make your backup -- would be as follows:

(1) Use the "Clear Data" button on the Settings page, Privacy & Security panel, Cookies and Site Data section

(2) Create a new blank profile (details below)

(3) Delete your "real" profile (details below)

Profile Swap

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Take a quick glance at the page and make a mental note of which Profile has this notation: This is the profile in use and it cannot be deleted. That is your current default profile. Make a note of the name for future reference.

Click the "Create a New Profile" button, then click Next. Assign a name like default-proton, ignore the option to relocate the profile folder, and click the Finish button.

Exit out of Firefox, and when you restart, it should launch into the new profile -- a brand new, uncustomized Firefox. Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system to keep it clean.

Return to about:profiles and find your old profile. Click its Remove button. In the confirmation dialog click "Delete Files" to remove your real profile data from the laptop.

Thank you so much. I appreciate the help. Would you mind terribly telling me exactly how to reverse all this when I get my laptop back? Please and thank you!

You can use the transplant procedure:

(0) Preparation

Set Windows to show hidden files and folders: https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

(1) Open Source Profiles Folder

Open the old Firefox folder from your backup and double-click into the Profiles folder. Hopefully you recognize one of these as the profile you want to restore.

Resize that File Explorer window with the source folder and move it to the left side of the screen.

(2) Open Destination Profiles Folder

Open the receiving folder using either step-by-navigation, or by pasting a shortcut in the Windows 10 system search box and pressing Enter to launch it:

• C:\Users\username\AppData\Roaming\Mozilla\Firefox\Profiles
• Shortcut: %APPDATA%\Mozilla\Firefox\Profiles

Resize that File Explorer window with the destination folder and move it to the right side of the screen.

(3) Drop a copy of the old profile folder back into the folder Firefox uses for profiles:

In the source Profiles folder on the left, right-click the profile folder (for example, abc1239z.default-release) and choose Copy. Important: copy the folder because you need to transfer the folder. This is not a method where you copy individual files.

In the destination Profiles folder on the right side of the screen, right-click an empty area and choose Paste to paste the folder here.

(4) Configure Firefox to use the old profile

Make a note of the text after the dot on the profile folder. You need the new profile name to match the old one in order for Firefox to regain use of your extensions and their data.

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

• Click the "Create a New Profile" button, then click Next.
• Assign the old profile name default and Firefox should show a proposed folder name with a new random part.
• Click the "Choose Folder..." button and select the old profile folder you copy/pasted so that Firefox picks up the full old name.
• Back in Firefox, click the Done button.

After creating a new profile, Firefox usually makes it your default profile (for external links and the next startup). To test, scroll down to it and click the Launch profile in new browser button.

Did it work?

If so, you're done.

If not, you can close that window without affecting your regular Firefox profile and change back to the profile you started with before this post. Click the Set as Default Profile button below your fresh profile.

Thank you so much for taking time to post this for me. My computer is on its way home so I will be doing this soon!