Defaults For Vector Content / Text In Affinity Photo | Revert | Factory
Select a design, any of the tools can be used such as rectangle and then go go to the fill and stroke settings in the control bar and then set to green or blue and set the stroke width to 30pt and set to dashed etc. Go to the edit menu and defaults and synchronize and then same menu but use the save command. They have been saved now, when you restart the application and then create a new rectangle or diamond then that width and fill and stroke etc will be used
You can do the same your font, font size, set other settings when you create artistic etc design. So if you want to use Arial Black then you can set that. If you want your characters to be initially 144pt then set to that. You can also use the rectangle tool etc and set the fill color and also the stroke and stroke width. Go to the same edit menu commands and synchronize as well as do the save. Restart the app and you will find them added using those new settings
Select the characters and go to the menu again but this time use revert and it will be reverted back to the previous setting. Go to the synchronize and save. Go to the diamond tool and create an object and repeat the revert and do the same, synchronize and save.
This takes everything back to the initial settings of the app. You don't need to initially select anything as they will all be reverted. However, if you want it permanent then go to each of the items such as a diamond and then use the synchronize and save and likewise the characters.
Sadly, it cannot be used for the gradient tool as that is black and white. That is a feature I would love to see added.