I'm having the same problem. I'm using Trial Version T18.0.3 R4 on MacOS 10.14.5.
Layout Designer "quit unexpectedly" every time I try to edit or create a template.
I've tried the fixes I've read on other threads here: clean uninstall and clean reinstall (three times), verify data, safe boot. Nothing is fixing it.
I've tried calling the number for mac desktop ([removed]) but so far I can't get through to a human.
Anything else I can do? Is there a known problem with this version and someone just needs to give me a link to a fixed version? Please help! Thanks in advance.