You can let cookies expire if you close Firefox and make an allow exception for cookies that you want to keep. You can't use Delete browsing, search and download history on Firefox if you want to keep specific cookies.

Tools > Options > Privacy > Cookies: "Keep until": "I close Firefox" --- CookieCuller: https://addons.mozilla.org/firefox/addon/82 Cookies are only protected within the CookieCuller extension, so do not use "Clear Recent History", but let the cookies expire if you close Firefox and protect the ones that you wish to keep.

Ccleaner besides being a great cleanup utility also has that ability in the "Options" section.

Firefox does not really do this. But you may use ccleaner to clear all cookies while keeping those in the to-keep list

www.piriform.com/docs/ccleaner/ccleaner-settings/choosing-which-cookies-to-keep

If you want to make login easier, try the addon "Secure Login" which login pages using saved passwords with one click. But remember to protect your profile with master password if you want better security for the stored passwords.