To all of you that are on Dreamweaver CC 2018 and are facing issues, please send me your Adobe ID, location, and phone number over a private message. We will get in touch with you for investigation. To send a private message, click my picture and use the Message button.
Read through this article, particularly the section for "Older versions of Adobe software (CS3–CS6)" + the comments section. Seems some users have CS5 apps running under High Sierra, however it seems the success various some.
The Adobe workarounds are typically a bit incomplete. You might also need to make some system changes on your Mac, including the Java implementation. You might also want to read this:
You're going to have to make some hard choices. The easiest solution would be to get a cheap Windows 10 laptop, because old versions of Dreamweaver will likely be good for at least a decade. If you can't, or won't, do that, you can revert back to a previous version of OS 10. Barring that, you can buy a subscription to the Creative Cloud.