> you can't open a project and one of it's dependent swift packages for editing simultaneously
You can. Any local packages are automatically editable in Xcode. Opening two projects referencing the same local package dependency isn't possible however.
>>willte+(OP)
Editor features for editable local packages are limited, even the project inspector hides some actions and then there is the whole story of schemas, working directory (maybe you want to tweak a binary or another target in that package) etc. It’s broken and frustrating.