I don't think you can associated a dynamic property (like a stretch action) to the width of an a attribute's value.
This would be a really nice feature, though!
An option would simply be to have the width of the block stretchable, perhaps with a few pre-set widths to choose from. If the att value's width exceeds the block size, it could be manipulated manually. Not the best option, but may be the best we can work with at the moment.
I look forward to seeing if anyone else has some suggestions!
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Chris Lindner
CAD Technology Consultant @ onebuttoncad.com
AUGI Board of Directors