Mount SSD partition into /tmp, /var etc

[mcfisto]

Hi guys,
sorry for maybe stupid question. I have RPi3 with SSD attached. I would like to mount SSD partitions into mount points that linux uses for frequently written data:
/tmp
/var

How to do that, please? I have looked at dietpi-drive-manager, but it allows me to mount just under /mnt. I have tried to edit /etc/fstab, but my changes are not applied and rewritten.

Maybe I am completely out of dietpi philosophy....please could you point me to some docs or give me an advice how to achieve that. Or is some better solution for my idea?

Thanks in advance.
D.

[Joulinar]

maybe you should consider to move the entire root FS to your SSD. Probably this post could guide you a little bit.

viewtopic.php?p=22717#p22717

pls ensure you have an external power supply for your SSD to avoid problems