This is a living post. Check back for updates as I learned more.
I find myself installing Qgis several times per year, and sometimes monthly (long story) and then spend the next day or two setting things up the way I like them. I knew that years ago the story around rapidly copying settings from one install to the next wasn’t perfect, but I recently looked at it again.
I believe that the current condition is better and looks like the following. It’s based on reusing a single directory that contains everything (I think) you need to redeploy Qgis with all your customizations. See 9.2 Work with User Profiles in the Qgis documentation for the authoritative information.
This paragraph from the docs is informative. The isolation, including installed plugins, is nice so that I can create profiles for the particular work that I’m doing and have the tools appear exactly as I like them for that job.
“As each user profile contains isolated settings, plugins and history they can be great for different workflows, demos, users of the same machine, or testing settings, etc. And you can switch from one to the other by selecting them in the Settings ► User Profiles menu. You can also run QGIS with a specific user profile from the command line.
Unless changed, the profile of the last closed QGIS session will be used in the following QGIS sessions.”
Here is the directory structure of a profile (settings) for the user SimpleUser. Since I stripped down the toolbars to make a simple data explorer out of Qgis, it made the QGISCUSTOMIZATIONS.ini file for me.
The user profile folder seems to contain all settings, plugins, and caches used by the user. To experiment I simply copied my default user folder (64MB) to CopiedDefaultUser.
and then chose that user under Settings/User Profiles
Here is the default user screenshot showing the toolbars and plugins installed
Here is the copied default user after simply copying the profile
When you switch between profiles, Qgis spawns a new instance under that profile name.
BTW, I spend about half my time in Linux (Ubuntu MATE flavor to be exact) and here is profiles look like in Linux - pretty much the same but under the user home directory under .local/share/QGIS/QGIS3/profiles/