1. Settings that should apply to all new shells (prompt, local variable settings, aliases) should go to S:shell-startup. To create one you can copy MOSSYS:s/shell-startup to S: and then modify S:shell-startup with the things you need.
2. The REXX: assign is a "defer"red type. This type of assign can't be added to, until the assign has been resolved. "dir rexx: >nil:" will do that, after which you can assign add to it. Or you can do what you did (remove, add both entries).
PS. Deferred assigns working like this was bit of a surprise to me. I would have expected "assign add" to resolve the assign and then add instead of erroring out. I might look into making Assign command do this. While this technically would be breaking compatibility with the original Commodore assign command, I think it might actually be desirable.
