Is there something in Gnome or Ubuntu 18.04 that will show the recent used GUI applications. For the command line commands there is the Bash History log which I use all the time.
If I can see a list, I can build a launcher to quickly launch a GUI from the recent list... saving lots of time in searching for a recently used application.
My current research is showing gnome activity journal, which might have had the feature, but it was discontinued and removed from the repository for Ubuntu 18.04.
I also believe this information is included in the Zeitgeist database, of which I'm researching how to extract it.
Cairo Dock has a recent event's app that has an application tab which shows a few of the applications that was run, but it shows less than one out of five applications that are launched.
Gnome panel has a feature called Frequent apps. You can enable it in the Show applications menu at the bottom of the dialog. By default, the applications menu shows all applications. When you press Frequent, it will show you only the applications that you frequently use by default.
I know it's not exactly what you wanted, it's not sorted from most recently used application to the least recently used one, if you use some applications regularly but not every day, they will probably appear in the list.
It seems that there's no support for Recently used applications out of the box, but the Frequent applications feature relies on some database that stores application usage. This can be enabled or disabled using the
gsettingsorg.gnome.desktop.privacy remember-app-usagekey. It might be possible to write a gnome plugin that relies on that data and adds another option to show recently used applications.