Adding an app is a no-brainer in Budgie DT settings. But anyone wanting to try stuff outside of Add Application and use Add Command instead, then, I've learned the possibilities get bigger.
If you don't know, here's what I self taught myself. It's small potatoes but you may find it valuable down the road.
Launch a text file at startup. Budgie Desktop Center/Add Command: gedit /home/joeblow/Desktop/logfile.text
Computer boots up and opens the document it right away...
so I thought what about an appimage I needed? it worked. Add command: /home/joeblow/Downloads/Coolprogram.appimage
---didn't even need a formal run command before the location.
just leaving it here. basically, so far, whatever I would have put in the terminal worked in the autostart command, so the variety of stuff you could autostart on boot just gets bigger with this command feature.
(Personally it helps me make sure some i's are dotted and t's are crossed before I go into full workstation mode in Solus.)