Said Phil :
On Mac, for some reason Laz uses ~/tmp by default,
Yep, same on Linux, Lazarus apparently makes that directory. I think it makes sense in a way, if Lazarus used /tmp the contents are blown away on reboot, might not be what user expects ?
Now that I understand what Lazarus is doing, I think its pretty good. Its a balance between getting you going quickly and keeping things safe enough. One improvement I'd like to see is some way of making the (new) user aware of the idea that a new, unsaved project is a "Test Application" and its save in the location indicated on the Options->Files ....
I have always used the simple trick of clicking "Save As" as a means of finding out where a file is initially but with a Lazarus Test Application that does not mention its existing path.