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Here's a copy and paste for terminal to set this up:

# Be sure to change:
# FOLDER_NAME   - the root folder name. 
# ACTUAL_PATH_TO_REAL_FOLDER - the path to the "real" folder.
# 
#    Example: 
#    "Drives    Users/bob/Documents/Drives"
#    .......^ this is tab (not spaces)
#    Both of FOLDER_NAME and ACTUAL_PATH_TO_REAL_FOLDER are not starting with /

sudo touch /etc/synthetic.conf
sudo chmod 0666 /etc/synthetic.conf
sudo echo "FOLDER_NAME  ACTUAL_PATH_TO_REAL_FOLDER" >> /etc/synthetic.conf
sudo chmod 0644 /etc/synthetic.conf
sudo chown root:wheel /etc/synthetic.conf

Here's a copy and paste for terminal to set this up:

# Be sure to change:
# FOLDER_NAME - the root folder name. 
# ACTUAL_PATH_TO_REAL_FOLDER - the path to the "real" folder.
# 
#    Example: 
#    "Drives    Users/bob/Documents/Drives"
#    .......^ this is tab (not spaces)
#    Both of FOLDER_NAME and ACTUAL_PATH_TO_REAL_FOLDER are not starting with /

sudo touch /etc/synthetic.conf
sudo chmod 0666 /etc/synthetic.conf
FOLDER_NAME='...'
ACTUAL_PATH_TO_REAL_FOLDER='...'
echo -e "${FOLDER_NAME}\t${ACTUAL_PATH_TO_REAL_FOLDER}" | sudo tee -a /etc/synthetic.conf
sudo chmod 0644 /etc/synthetic.conf
sudo chown root:wheel /etc/synthetic.conf
/System/Library/Filesystems/apfs.fs/Contents/Resources/apfs.util -t

The apfs.util -t command should allow modifications without requiring a restart, but if it does not work then a restart should make the new entries appear at root.

Here's a copy and paste for terminal to set this up:

# Be sure to change:
# FOLDER_NAME   - the root folder name. 
# ACTUAL_PATH_TO_REAL_FOLDER - the path to the "real" folder.
# 
#    Example: 
#    "Drives    Users/bob/Documents/Drives"
#    .......^ this is tab (not spaces)
#    Both of FOLDER_NAME and ACTUAL_PATH_TO_REAL_FOLDER are not starting with /

sudo touch /etc/synthetic.conf
sudo chmod 0777 /etc/synthetic.conf
sudo echo "FOLDER_NAME  ACTUAL_PATH_TO_REAL_FOLDER" >> /etc/synthetic.conf
sudo chmod 0644 /etc/synthetic.conf
sudo chown root:wheel /etc/synthetic.conf

Here's a copy and paste for terminal to set this up:

# Be sure to change:
# FOLDER_NAME   - the root folder name. 
# ACTUAL_PATH_TO_REAL_FOLDER - the path to the "real" folder.
# 
#    Example: 
#    "Drives    Users/bob/Documents/Drives"
#    .......^ this is tab (not spaces)
#    Both of FOLDER_NAME and ACTUAL_PATH_TO_REAL_FOLDER are not starting with /

sudo touch /etc/synthetic.conf
sudo chmod 0666 /etc/synthetic.conf
sudo echo "FOLDER_NAME  ACTUAL_PATH_TO_REAL_FOLDER" >> /etc/synthetic.conf
sudo chmod 0644 /etc/synthetic.conf
sudo chown root:wheel /etc/synthetic.conf

Here's a copy and paste for terminal to set this up:

# Be sure to change:
# FOLDER_NAME   - the root folder name. 
# ACTUAL_PATH_TO_REAL_FOLDER - the path to the "real" folder.
# 
#    Example: 
#    "Drives    /Users/bob/Documents/Drives"
#    .......^ this is tab (not spaces)

sudo touch /etc/synthetic.conf
sudo chmod 0777 /etc/synthetic.conf
sudo echo "FOLDER_NAME  ACTUAL_PATH_TO_REAL_FOLDER" >> /etc/synthetic.conf
sudo chmod 0644 /etc/synthetic.conf
sudo chown root:wheel /etc/synthetic.conf

Here's a copy and paste for terminal to set this up:

# Be sure to change:
# FOLDER_NAME   - the root folder name. 
# ACTUAL_PATH_TO_REAL_FOLDER - the path to the "real" folder.
# 
#    Example: 
#    "Drives    Users/bob/Documents/Drives"
#    .......^ this is tab (not spaces)
#    Both of FOLDER_NAME and ACTUAL_PATH_TO_REAL_FOLDER are not starting with /

sudo touch /etc/synthetic.conf
sudo chmod 0777 /etc/synthetic.conf
sudo echo "FOLDER_NAME  ACTUAL_PATH_TO_REAL_FOLDER" >> /etc/synthetic.conf
sudo chmod 0644 /etc/synthetic.conf
sudo chown root:wheel /etc/synthetic.conf