Install 10.15 beta on external drive?

Yep works like a champ. using it now. Format your extneral drive as AFPS, select it in the target of the installer and you're off

I did it. It is possible, but multi-step. I have not found a 'full install' download for 10.15 so this is what i did:

1. in your 10.14, open app store

2. download 10.14 macOS (you will get the ~6GB install file)

3. run the install for 10.14 and install a fresh / clean 10.14 on your EXTERNAL drive

4. boot into that version of 10.14

5. use the Apple developer page to install the certificate needed for 10.15 beta

6. in the System / Updates you should then see the option for 10.15 beta

7. install it on your external drive, over the fresh new 10.14