Is there a systematic way to determine and display to a user the last date/time they logged into the application?
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As other practitioners mentioned there is a way to retrieve last time user logged in via this plugin. Use that and customize user record to display the timestamp, Edit User Record Type.
After looking at the source code for this plugin it looks like it has some limitations.
There is another plugin which might help in getting all data. You can either customize it as per your requirement or do a work around over that plugin.
https://forum.appian.com/suite/sites/shared-components/page/shared-components/record/lMBCLGOdlMUpdGVqW3dQaIKmclBmvvNEj8vu_cjb7T-5YiPr4Fu8ly5Yj1s09uenE4RYzA8zKyx7eiUhe6kLnOxfeDHIMtA4tsrAWoZamIDmUAYiQ/view/summary