Syntax highlighting requires blank between ⋄ and :endif

[mbaas2]

Does not color ...⋄:endifcorrectly.

[aplteam]

Well, putting ⋄ and control structures on the same line is a very bad idea. So, rather putting an effort into "fixing" this my advice is: don't do this.

As long as the Dyalog debugger does not process diamondized lines properly, putting them on one line defeats the whole purpose of control structures: you won't see which code is executed and which isn't.

[mbaas2]

I agree that a better handling in the tracer would be nice. But I disagree with the conclusion about not fixing this.
NB: This would also affect cases like

:if Condition
   DoThis ⋄:endif

which are frequently use. That can be traced/debugged just fine, but the syntax colouring does not kick in for the 2nd line.