Take ownership of /mnt/ using Rootactions from Dolphins’s rightclick menu
Create my mount folders
launch Gnome-Disk
select one of my secondary drives
Rightclick on one of the new folders and select Copy Location
Click one the corresponding drive name in Ghome-Disk
Selecect it’s settings
Select Edit Mount Options
Toggle off Use Session Defaults
Check Mount on startup
Hi-lite and replace the location in Mount Point with the path of the folder you copied from /mnt/
Save
Mount