I don’t need automatic builds for each commit, but I would like to be able to easily trigger builds when i want without having to log in, go through the dashboard etc.
Have you considered making a bot for slack, so you could just tell it to build a certain project then it informs your service via the api?
How about an IFTTT recipe, allowing you to select the project? Then you could link their Do button app or an external IOT button to trigger builds for your project.
I use separate branch for cloud builds, it’s much more controlable and allow to continue working and commiting while build runs. All you need for triggering build is just pull changes from your branch into “cloud-build” and push it.