Hello ; Every user's information are so valuable to us so the logIn process is so important and it has to be performed every time a user try to access his account. You can save your information to your browser so this will facilitate the process just a solution but I don't recommend this. Note : I don't recommend to save your personnel information to any browser so just follow the long secured process instead of trying unsecured  method. Thank you for sharing this, it will be well considered.

@JLCPCBsupport most websites I frequently access will keep me logged in (facebook, google, amazon, etc.). Your site also keeps me logged in, however with easyeda, jlcpcb, and lcsc, they require a click the "sign in" button. I don't get asked for credentials. Whatever process you have in the "sign in" page that detects the cookie, should be placed on all of your page loads.

@EdHayes3 Thank you for your comment, well considered :)