I wish ability to use local values that will not be saved, only used i local compilation of code. Specifically when setting password such as in Wi-Fi sketches where User, Password, IP, DNS and MAC should never be stored publicly.
One way could be to have a protected "credentials" page in your Arduino profile where values can be changed and stored and never by mistake be uploaded or stored in public code. Another suggestion is ability to add a tab "locked.h" for temporary storage of sensitive values and have that tab server-side encrypted salted with user Arduino Create credentials.
Values from a "credentials" entry or "locked.h" file could be linked in sketch with a reference like "//securevalue:p14" when stored and replaced with secure value reference p14 (Password number 14) during compile.