I understand that Disks can be optioned to mount device on boot / start.

How can I use Disks or other application to change mount at "run time" ?

I am not that comfortable messing with fstab.

Cheers

Yes disks can be mounted dynamically, this is what occurs when you attach a USB drive.

I believe the best way to handle this is using the command line and editing fstab.

Yes, I did read "how to choose distribution...

I am totally flustered with the latest Ubuntu 20.04.2

Can anybody point out the major differences between Debian and Ubuntu?
( I rather switch then fight...)

I need RELIABLE OS to write C/C++ code - run IDE likes Eclipse and QtCreator.
I could careless for social media applications.
I also like open forum with reasonable participation.

Ubuntu is NOT open forum - it is "privilege" to post there...

So is Debian a good choice ?

I used to run Debian and liked it very much. Ubuntu was based on it, so Debian is more mainstream. It comes in three varieties, Stable, Testing and Unstable, so you can choose the degree of software novelty you feel most at home with. But Debian now uses systemd, which a lot of people here hate. If you want a Debian variant that uses sysvinit, there is Devuan.

Hazel described the situation pretty well. However, Ubuntu is now pretty much a resource hog.
Older hardware? Try Xubuntu (XFCE WM, I have used before with much better performance on my older hardware.) or Lubuntu (LXDE WM). If hardware is the issue, These may be better options than Debian.
Want real lean and mean? try bodhi (used happily for several years)

As to the original question, working in fstab can be scary at first, but it is not too hard to become knowing about it. Most distros now set up drives so accessible (if during install a drive is seen, it is configured to be mounted so you can access with the file manager.)Did your install not do this? Trying to mount a DVD drive? Working with the man pages for mount and fstab can give you the info that you will need to your specific issue.

Editing existing lines in fstab is more frightening nowadays because they use UUIDs instead of device names and it makes the whole thing look more difficult and obscure. Adding lines is easier because you can use the device names or your own labels, which is what I do.

When I have to edit any file in /etc, I always start by making a copy with the .orig suffix. That way, if my edited version (or any subsequent one) doesn't work, I can always get back to what the distro's installer provided. Also, it allows me to see at a glance which files I have personalised.

Some people recommend keeping a notebook into which you enter all changes of this sort.

Define "mount dynamically".

Does it mean you mount manually in a running system as opposed to mounting boot time? Nothing is easier, in particular if you have it already in fstab. Otherwise you need superuser rights and the command line must be complete.

Or you mean automounting when devices are mounted automatically when accessed? There are several ways to accomplish this. A quick net search will bring up all tutorials you may need.

The question is no longer about how to mount dynamically?

You can try before you switch, using VM or live boot.

Only you can decide if a distribution is right for you.

Would it be too impertinent to ask you to once a while contribute instead of just waste your talent preaching?

Simple - I have stuff , C/C++ code build in SPECIFIC OS files.
To access it in currently running OS, which keeps changing with each new version install ( version upgrade takes way to long, new install from ISO is much faster )
I need to change mount points - hence dynamic mounting.

As explained above - auto mounting does not work for me. I had some luck with "sudo -i commomand"


BTW Disks does have an option to mount "on the fly" . My big isse is I cnnot get Disks to always execute - it will time out. I am hoping next Ubuntu version will work better.

Another possibility would be a bind mount. This is where you have a disk mounted on one directory but you bind another (preferred) directory to it as and when required. You can do that with mount using sudo.

Here is a simpleton view of this.

Application "Disks" ALLEGEDLY updates fstab.
true or false?

I have a great respect for hackers fluent in using CLI.
However, I also subscribe to KISS principle.

If GUI , in this case "Disks" really updates fstab - why bother ?

Put simply, per your request:
True. Yes the Gnome Disks application can do this.

There's a gear icon to edit disk options where you can tell to either auto mount versus not, you'll want to set it to not.