Insomniac Browser now has session restoration: one can close Insomniac Browser and, after the next Startup, continue where one has left off.
That setting is switched on by default for all users and is located here: insomniac://settings/onStartup as “Continue where you left off.”
However, one could change it to “Open the New Tab page,” which should disable the session restoration feature in Insomniac Browser and function like older versions. The “Open a specific page or set of pages” option will allow you to open pre-defined pages at every Startup.
Only “Continue where you left off” restores all data, fingerprints, and proxy settings.