While once again being annoyed by the obnoxious way modern GNOME handles in-application dialogues (fx. Nautilus’ Properties dialog) as modal (ie. freezes the parent window) AND even prevents movement of the dialogue relative to the parent I did some searching which revealed a partly solution!

This was also complained about in a 2017 LibreOffice bug report which concluded that the immobility is a GNOME 3 desktop default behaviour caused by the setting attach-modal-dialogs.

Details in the related GNOME bug report shows how to disable this by modifying gsettings;

In a regular upstream GNOME session, `gsettings set org.gnome.shell.overrides attach-modal-dialogs false`, a schema of ‘org.gnome.shell.extensions.classic-overrides’ for the classic session and afaik ‘org.gnome.mutter’ for a Ubuntu-patched GNOME.

Now knowing which term to search for, lots of discussion about this shows up (including posts similar to this), the best write up of the mitigation is probably this askubuntu question. And the mother opinionated Ubuntu bug report is this where Ubuntu officially states;

We do not consider Gnome’s defaults in this area unreasonable.

But the reason for this behaviour? Seems to be unknown as even this 2018 bug report on gnome-shell hasn’t received any official answer or comment about why this would be a sane default. Go figure…

TLDR;
On Ubuntu 20.04 and similar distributions turn off GNOME’s attach-modal-dialogs feature by doing;

$ gsettings set org.gnome.mutter attach-modal-dialogs false

Or if you like the mouse; install & launch gnome–tweaks and click “Windows” -> “Attach Modal Dialogues”;

Oh, and remember to read the Nielsen Norman Group article “Modal & Nonmodal Dialogs: When (& When Not) to Use Them” (summary: Modal dialogs interrupt users and demand an action. They are appropriate when user’s attention needs to be directed toward important information).

Edit:
2023-07-30: add gnome-tweaks approach

This post will detail some stuff I’ve done to a plain Ubuntu 18.04 Desktop (bionic) to make me feel a little more at home in the transition from my daily driver for years the 16.04 release using Canoncial’s Unity as the primary desktop interface to the GNOME Shell of 18.04. Canonical abandoned the former after shifting focus from the convergence and personal device market to cloud and IoT in 2017 leaving development of its mobile OS, Ubuntu Touch which Unity is a part of, to the community formed UBports project (Unity8 is now known as Lomiri). I’ve been putting off this transition exactly because I knew it would require me to make some tweaks to my daily routines, but this system is not one I use on a daily basis so it will make the transition a gentle ride.

The intention is to update this as the experience progresses.

EDIT 2021-08-25: clean up and publish dormant draft post

Browsing GNOME Extensions

To be able to install GNOME Extensions directly from a browser while perusing the directory at extensions.gnome.org, add the GNOME Shell Integration extension/add-on to your browser (Firefox add-on, Chrome Web Store), then install the Integration extension in GNOME to communicate with the browser extension:

sudo apt install chrome-gnome-shell

After this you can go to extensions.gnome.org/local/ to see, configure and update installed extensions.

Useful GNOME Extensions

• Clipboard Indicator (source): access clipboard history
• Better Volume Indicator (source): adds scroll to adjust and middle-click to un/-mute
• Fuzzy Clock (source): changes time in notification area to textual clock
• Alarm Clock (source): shows alarm notifications for gnome-clocks (see below)

Time Keeping

World/Alarm/Stopwatch/Timer application

GNOME includes a nice Clock application which is available in the package repository but not installed by default;

sudo apt install gnome-clocks

Installing the Alarm Clock extension described above, will also show the application’s alarms in the notification area.

Notification bar

I like both the date and seconds to be displayed in the head of the desktop, so to format the text a couple of extensions are available;

• Clock Override (source)
• Panel Date Format (source)
• Datetime Format (source)
• More options described here, ;
  • https://askubuntu.com/questions/1096203/how-to-display-custom-formatted-clock-in-top-bar-on-multiple-displays-in-ubuntu
  • https://superuser.com/questions/573951/how-can-i-show-the-date-in-the-gnome-3-menubar
  • https://askubuntu.com/questions/968860/how-do-i-customize-the-date-time-display-in-gnome-shells-top-bar