Unfortunately you can’t just copy and paste buttons from one place to another and I didn’t find any way of setting the default from Arial, auto etc to something else. But what you can do is to copy the properties you have set for an object (eg button) from one object to another. In the case of a text only button this is how:
Insert a first empty text only button in your project to use as a master and set the text style, size, etc as well as transparency, colour and position etc to your requirements. Right click on the newly created button and select copy.
Insert another empty button where wanted in your project and give it the style you want eg text only. For some reason this style choice cannot be copied…. Right click on the new button and, in the menu “paste attributes”, select the attribute you want to copy or just “all”. Depending on what you select, the appropriate properties are copied to the new button including it’s transparency and position which is great for getting your buttons placed in the same regular place.
This does make it a lot faster than creating each button from scratch although it whould have been nicer to be able to just copy a button and then “paste in place” like can be done in a lot of software.