I've found two issues when migrating Effects.
1) I'm struggling with the c2id again. If the new id matches C2, then everything is fine. However, for the sake of completeness, the documentation says if the id does not match the old one, c2id is used when importing C2 projects. (I don't actually understand the rest of the c2id description; I think that should be reviewed/clarified). I've tried implementing this, but it doesn't work. I've checked the tag used in the C2 file, and set the c2ids to match (just seem to be the lowercase Name tags), but trying to open a CAPX results in "Failed to open project. Check it is a valid Construct 2 single file (.capx) project." The same file will open if the id tags do match the old.
2) This is definately a bug: if a comma is missing from the language JSON file in the parameters data (ie: between name & desc), the addon fails (as expected), BUT it continues to fail in "safe-mode", which means you have to wipe out the cache again to recover.
c2id: http://www.blackhornettechnologies.com/Construct3Stuff/Bugs/C3EffectIssue.zip
This has my C2 effect files, my attempt at converting to C3, using c2id to match the C2 definition, and a CAPX using the effect.
safe-mode break: http://www.blackhornettechnologies.com/Construct3Stuff/Bugs/badC3bht_setcolor4_test.zip