This would entail allowing a logged in user to set a different Safe Search setting on each of their logged in devices. It would mean that for each new device they log in to, they would need to make a choice about the Safe Search setting state (I think other search engines default to enabled on a new device to be on the safe side).
The use case here is to allow users unrestricted search results on their personal devices, while filtering on a company device to avoid accidentally seeing NSFW content at work. Because one needs to be logged into Kagi & pay for the subscription on each account, and the account itself holds the Safe Search preference, this is not currently possible without paying for two subscriptions on two accounts (as far as I can tell).
When logging into Kagi on a new device or browser, Kagi would default to Safe Search being enabled. If a user chooses to disable Safe Search, it would only affect the experience on that device & browser combination. I believe Kagi would need to store some data of the modified setting within the browser.
Google defaults to Safe Search = blurred images, DuckDuckGo defaults to Safe Search = moderate if the user has not previously chosen to change the Safe Search setting for that device & browser.