Yes, It is. I have an ongoing association and could edit shoe colors, set injuries etc.
First, open up the horizon and drag your file onto that empty area and click on contents tab you'll see the file that has the same name as your asss file. Right click on that, extract it to a folder, fire up the leftos editor with ''recalculate crc on save'' box checked and pc ret mode(If you're using the default roster aka out-of-box roster. Most rosters on here OS use the default roster as base i.e sim-world. If not, you have to select custom mode) Anyway, do your edits then save. Now launch the hex workshop, open up the file you've just saved and select the fifth byte, press ctrl+shift+end at the same time, options tab - generate checksum - select algrorithm: CRC (32 bit) - hit generate. Save the file. Now back to the horizon, again on the contents tab, right click on the 'root' file, this time select replace with the file you've edited, then save,rehash, and resign, and you're done.