It is not possible to do.
Linear and Elevation Dimension types cannot be converted back and forth. You will have to recreate the Dimensions.
If you would like this functionality, please create a wish for it.
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac27
