You can but I wouldn't recommend it at this point. To create a blank mode navigate to the "modes" folder inside the Vectr directory and drag/drop the modes into an alt folder, this will cause vectr to boot up without any modes in your list, and thus creating a blank canvas. The twist here however is that when you do this it puts every setting at max and even gives you access to some options that you don't usually have access to, so it's very confusing.
What I've done is created my own "new project" mode and when I'm starting to develop new firmware ideas I empty the modes folder like before but I leave this one inside, causing vectr to boot up in the way I like it. My recommendations for new projects are to drop all color options down to 1 color, and to set all threshold bar values to 64 (for both bars). This gives you the most basic setup to experiment with only one color per set and zero thresholds to worry about. Here you can easily adjust strobe/blank times to see how big, small or wide your patterns are, I've got my own favourite strobe values and you'll develop your own too. As you would like, perhaps slowly add more colors and introduce a threshold (solid/overlap) to see how your light changes, build up little by little from there.
I have some work I need to finish over the weekend but once I get that out of the way I'll write some basic 101 and more advanced/intermediate tutorials up that will help you make more modes, have a look in the mode swap forum for examples of what I'll be using as examples in the tutorials.