Operating an offset function to a line, the both sides option is not kept between operations.
That is, you have to reselect each individual line, then select the both sides option again and again. Also it is impossible to select a group of lines and apply the double sides offset to all of the at once.
.F
Yes, it is this way also in the Windows version of Rhino. Don’t know why this option is not “sticky”.
Yes, same as above. Offset does not take multiple curve inputs - I’m assuming because the results would be unpredictable if all the curves are not planar. So for this you currently need a script. Unfortunately, my current multiple offset scripts are all programmed in VB, so they do not run on Mac; and I haven’t time to convert them to Python for the moment.
–Mitch
Nothing too unpredictable if you offset a group of lines both sided, i guess.
Yes, if they’re all only lines. But you can offset any kind of curve in Rhino, so the command has been tailored for the general case.
– Mitch
I had some time to “translate” my offset multi-curve 2 sides script into Python. Attached below. I have NOT tested it on Mac yet though…
Offsets open and closed planar curves both sides, with choice of end style for the open curves. Both open and closed curves can be run together. Non-planar curves will be refused; lines will use active view CPlane, so make sure the view you want is active. Should remember the last-used settings.
Can’t guarantee that the ends will always work. Also Offset is in itself not extremely unreliable, so some types of curves might fail or offset incorrectly. Use at your own risk… 
–Mitch
OffsetMulticrvs2SidesWEnds.py (5.7 KB)