FIRST

• Create a file where to put your script, for example:
  MY_SCRIPT.sh

Then inlcude the code:

#!/bin/bash

TIMESTAMP=$(date +"%Y%m%d_%H%M%S")

# Initialize an array to store issues
issues=()
success=()

# Define source paths with placeholders
SOURCE_BASE="C:/Users/%USERNAME%/AppData/Roaming/Opera Software/Opera Stable/Default"
SOURCE_SESSIONS="$SOURCE_BASE/Sessions"
SOURCE_SESSION_STORAGE="$SOURCE_BASE/Session Storage"

# Define backup destination with placeholder
BACKUP_DIR="D:/%PATH-TO-DESTINATION%/Opera/session saves/$TIMESTAMP"

# Create backup directory
if ! mkdir -p "$BACKUP_DIR"; then
    issues+=("Failed to create backup directory.")
else
    success+=("Backup directory created successfully.")
fi

# Create session directories
SESSIONS_DIR="$BACKUP_DIR/Sessions"
SESSION_STORAGE_DIR="$BACKUP_DIR/Session_Storage"
if ! mkdir -p "$SESSIONS_DIR"; then
    issues+=("Failed to create Sessions directory.")
else
    success+=("Sessions directory created successfully.")
fi
if ! mkdir -p "$SESSION_STORAGE_DIR"; then
    issues+=("Failed to create Session Storage directory.")
else
    success+=("Session Storage directory created successfully.")
fi

# Copy session files
if cp -r "$SOURCE_SESSIONS/"* "$SESSIONS_DIR"; then
    success+=("Successfully copied session files to $SESSIONS_DIR")
else
    issues+=("Failed to copy session files.")
fi

# Copy session storage files
if cp -r "$SOURCE_SESSION_STORAGE/"* "$SESSION_STORAGE_DIR"; then
    success+=("Successfully copied session storage files to $SESSION_STORAGE_DIR")
else
    issues+=("Failed to copy session storage files.")
fi

# Set permissions for the script
chmod 400  "%YOUR-PATH%/%MY_SCRIPT%.sh" # Read owner, no write, no execute

if [ $? -eq 0 ]; then
    success+=("Permissions set successfully to read only for script and user.")
else
    issues+=("Failed to set permissions.")
fi

# Log file creation
LOG_FILE="$BACKUP_DIR/backup_log.log"

# Log issues and successes
if [ ${#issues[@]} -eq 0 ]; then
    echo "# No issues reported during backup process." >> "$LOG_FILE"
    echo "No issues reported during backup process."
else
    echo "# Backup process completed with following issues:" >> "$LOG_FILE"
    echo "Backup process completed with issues: see log file for details."
    for issue in "${issues[@]}"; do
        echo " - $issue" >> "$LOG_FILE"
    done
fi

if [ ${#success[@]} -eq 6 ]; then
    echo "## Fully completed backup process, success of the following process:" >> "$LOG_FILE"
    for success in "${success[@]}"; do
        echo " - $success" >> "$LOG_FILE"
    done
else
    echo "## Backup process incomplete, success of the following process:" >> "$LOG_FILE"
    echo "Backup process incomplete, see log file for details."
    if [ ${#success[@]} -gt 0 ]; then
        for success in "${success[@]}"; do
            echo " - $success" >> "$LOG_FILE"
        done
    else 
        echo "## Backup process incomplete, no success to list!" >> "$LOG_FILE"
    fi
fi

# Final messages
echo "Backup process completed to:"
echo "$BACKUP_DIR." 
echo "See backup_log file in created folder for details about issues or success."
echo "Opening directory..."
explorer.exe "$(cygpath -w "$BACKUP_DIR")"
echo "Goodbye!"

Notes:

• Replace %USERNAME% with your Windows username.
• Replace %PATH-TO-DESTINATION% with your desired backup destination path.
• Ensure you have the necessary permissions to run the script.
  (Use on the MY_SCRIPT.sh file that contains the code:
  chmod +wx MY_SCRIPT.sh).

Then, run with this command:
./MY_SCRIPT.sh

You should see the completion messages in the terminal and explorer should open in the created folder.
Edit the code if you want to open folder differently or not at all and the log file created.

1. Copy the contents of "Sessions" folder (while Opera has your open tabs/workspaces)

(For WIndows 11)
C:\Users[YOUR WINDOWS
USER]\AppData\Roaming\Opera Software\Opera Stable\Sessions

2. Paste/Backup the contents into another new folder/USB drive of your choice

At any point, should you lose the open tabs in Opera.

3. Delete all the contents of the "Session" folder

4. Paste the "Backup" version of contents from step 2.

5. Open Opera and you should have your tabs/islands/workspaces
   back again!

6. Backup your "Session" folder every time you have new tabs, islands or workspaces.
   Or whenever you feel the need to backup your Opera open tabs.

7. Request Opera to have this feature built into the browser for saving sessions!

You have to save each open tab only once. And in case of a crash or Opera goes blank/forgets your open tabs. The pinboards would have your manually saved open tabs.

@yaakhan I'm looking for the same function, did you solve it by any chance?

No I haven't. I had raised it to Opera support team via the "Suggestion" section and a team member marked my request as "Invalid".
Which is very sad for an Opera user like myself.