I was wondering if it was possible to login to different salesforce environments (Sandboxes, scratch orgs, production env, etc) using either Apex/LWC/Aura (or anything that I can make a quick action to). For example, I have a list of credential records, with the username and password, and I would like to have a login button that creates a separate tab that can automatically redirect to that specific instance and log in.
Currently, if a user wants to login to a particular instance, they have to either go to test.salesforce.com or login.salesforce.com (depending on if it's a sandbox or production) manually, then copy the password and username in. The ideal situation is to have a login button that can do this automatically from the record page where the username and password is located.
I think previously this could have been accomplished through the URL, but salesforce has recently patched this out due to security concerns. Is there another good way to do this?
It sounds like you're trying to solve two specific challenges:
The clear solution, in my mind, is to use the OAuth Web Server flow to execute initial authentication and then store the refresh token that results from this flow. This token survives password resets, and may be used more or less indefinitely to create new access tokens - which users can then use to log in via a frontdoor link.
There's an out-of-the-box tool that does this already: the Salesforce CLI. You can authenticate orgs to its toolchain, name them, and subsequently access them with a single command (sfdx force:org:open). Users that prefer a GUI can access the exact same functions in Visual Studio Code.
If you're hellbent on doing custom development to handle this use case, you can, but you need to be very careful of the security implications. As one example, you could implement an LWC + Apex solution that executed the relevant OAuth flows against orgs and stored the resulting data in an sObject, then allowing users to click a button to generate a new access token and do a one-click login.
But... if you do this, you're storing highly sensitive credentials in an sObject, which can be accessed by your system administrators and potentially other users who have relevant permissions. That data could be exfiltrated from your Salesforce instance by an attacker and misused. There's all kinds of risks involved in storing that kind of credential, especially if any of them unlock orgs that contain PII or customer data.