ST3 Crashes when I edit info.plist

[PedroL]

I have tried to edit info.plist to add some file types and icons so that ST3 will manage them. But whenever I do this, update LaunchServices with lsregister, and restart, ST3 will not launch (and I get a report for that). The changes are as minimal as adding “text” into the extensions assigned to Markdown. I use a Mac.
I used to sort this out with 10.14 by editing the plist, using lsregister, and then changing back the plist to the original one. This changed the icons I wanted, but would not make ST3 to crash. However, this does not work with 10.15.
Any ideas will be most appreciated.