joplin/readme/apps/profiles.md

Multiple profile support

To create a new profile, open File > Switch profile and select Create new profile, enter the profile name and press OK. The app will automatically switch to this new profile, which you can now configure.

To switch back to the previous profile, again open File > Switch profile and select Default.

Note that profiles all share certain settings, such as language, font size, theme, etc. This is done so that you don't have reconfigure every details when switching profiles. Other settings such as sync configuration is per profile.

The feature is available on desktop and mobile.