Some users already have a sandbox page at a different location from the default, and have set up a redirect from the default sandbox location to their custom sandbox location so that clicking on the "Sandbox" link enabled by the SandboxLink extension takes them straight to their custom sandbox. For example, I have [[ https://en.wikipedia.org/w/index.php?title=User:Mr._Stradivarius/sandbox&oldid=480763292 | User:Mr. Stradivarius/sandbox ]] set to redirect to [[ https://en.wikipedia.org/w/index.php?title=User:Mr._Stradivarius/Sandbox&oldid=659215747 | User:Mr. Stradivarius/Sandbox ]]. However, the extension [[ https://git.wikimedia.org/blob/mediawiki%2Fextensions%2FSandboxLink/bd4dabb1f9e0146f671d1336814579a12d9f5bf4/SandboxLinkHooks.php#L43 | doesn't follow redirects ]], which means an extra click and an extra page load before users doing this will reach their sandboxes. Unless there is a pressing reason not to, I think we should change the extension to always follow redirects so that user sandbox locations can be more customisable.
See [[ https://en.wikipedia.org/w/index.php?title=Wikipedia:Village_pump_%28technical%29&oldid=662523453#Extra_sandbox_link_in_my_top_menu | this Village Pump discussion ]] for another example of a user doing this.