The launcher does not save the profile's specified window resolution. launcher_log.txt attached. This only started happening for me in the past couple of weeks.
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Minecraft Launcher version: 2.3.508-1.1.28
As per MC-231366, this bug also affects the survival mode inventory.
When you are in inventory and are holding one or more items with the pointer/cursor, it used to be that if you exited the inventory by pressing "e" or "Esc", the item would drop. This is no longer the case - the item returns to the inventory.
I concur with natebc. After the launcher autoupdate to version 2.3.520, I no longer have the forgotten resolution problem.