Thank you, @David_Cox. I hope we can locate the final release of CrossBasic, though: the link you shared contains (as of writing) only the earlier “DR1r7” release I mentioned in my post, rather than the latest version.
Looking at @Geoff_Perlman’s screenshot of CrossBasic that he shared in another thread, it seems the final release of CrossBasic was CrossBasic 1.0. Notice how, for example, on the top-right corner, the app even has a unique icon on the Apple Menu (the icon of CrossBasic), whereas the older “DR1r7” release contains a different, generic app icon in a screenshot of that Macintosh Repository page.
Could it be Andrew (the original author of CrossBasic, Andrew Barry) is still reachable somewhere, somehow? Maybe he would have a copy of his final shareware release?