"Anyway i think this topic is nonsense, when you are using an USB Stick and complain it is slow. Usb sticks are in general slow..."

Please, read carefully what my problem is before commenting
It has nothing to do with the speed of usb flash sticks.
I use a usb flash because I have to, for various reasons. And, by the way, have not had problems with ext2 on a flash , I use them for at least 8 years and before starting using ext2, I did testing , I formatted the same flash to fat32, ext2 was speedier.
The problem is not the speed of the usb . The problem is that when i try to "save as" an archive, a list of all archives in the directory appears where arcives are been sorted. It is done BEFORE hitting enter and give the final new name. It doesnt sound like a good idea for me as it is a slow procedure. And, lets say I do a typo as I type the new name. I have to delete the typo and meanwhile a new sorting strarts etc.
It should be simpler (as it was done so far in older Ubuntu versions) to enter the final name and then the system sort it in its final position.

are you actually doing any research yourself while we discuss it here?
look at the dependencies of the applications in question.
on my system, libreoffice optionally depends on gtk3.
i guess this means it uses the gtk3 file save/open dialogs if available.
i seem to remember foggily there was an option to use "native" (meaning qt) dialogs.
and so on, for all applications/packages affected by this.

generally speaking, ext2 is ... unusual, and outdated, have you even tried using fat32 instead?

also generally speaking, linux distros, and especially ubuntu, tend to get more bloated over time - just like windows.

FAT32 on USB with 16,000 files in a single directory???

The problem lies with not using a sensible sub-directory structure, aggravated by using a slow physical medium.

ok, the fact that it's all in one directory went totally over my head.
in that case, forget EVERYTHING i said so far.

Finally, I found the culprit. Everything was corrected after uninstalling libreoffice-gtk3 and installing libreoffice-gtk2. It also made libreoffice, faster. Interestingly, the "pixalated" appearance of jpeg scanned images I included in my .odt docs, appeared again (as they used to be in ubuntu 14.04 and 16.04, with libreoffice-gtk3, they appear much smoother, this is the only downside I can spot, not very important to me.

ext2 is awful - in fact the kernel devs seriously considered dropping it altogether. ext4 can be used without a journal if you insist - at least that way you get the benefits of a more modern codebase.

Try using xfe for the file rename - I found it much quicker than the filemanagers shipped with the major DEs.

Edit: - oops; didn't see these later posts ... my bad.

Hi syg00
As a matter of fact I use pcmanfm, it is lightning fast too as compared to nautilus and dolphin. I will give xfe a try.
About your suggestion - ext4 without journalling- it is sounds like a very good idea. I will do a small test if it responds faster than ext2 and let you know

As I promised, I did a small speed test : vfat vs ext2 vs ext4 (with and without journal)
I measured the time it takes nautilus to open a directory (900 mb) with 16600 odt docs to the same flash drive formatted to the above filesystems. I used the same usb port and the pc wasnt doing other jobs at that time, I also opened a top command to check there was no other resource heavy processes
Time was for vfat 52 seconds , whereas for ext2 and ext4 with and without journal 2,7 seconds
So, ext2 appears to be as fast as ext4 and vfat tooo slow at least for this particular task.

This is not a surprise - except that the sluggishness of a flash stick obviously didn't wipe out any sensible comparison.
Keep your data on disk or SSD but take periodic backups.

If you like, you could use multiple USB sticks and write the backup date on the stick.