Hidden files

By default Dopus comes up with hidden folders not shown.
Can I change so by default they are on?

Yes. If you're using the default toolbars, you can find the two commands in the "menu" toolbar. It's under the fifth icon from the right, where the info tip says "folder options", when you hover the mouse cursor over that icon. In there, you can find both commands, to toggle the hidden files, as well as the hidden system files.

I have a button set with Set HIDEFILTERATTR h, which I think toggles, but Dopus start up with the files hidden.
I'm looking for a way to start up not hidden.

Alternativley you can check out your settings in -> preferences -> folders -> global filters, where you can find two options concerning the hidden state. If they are both checked, you could try, if unchecking them solves the problem.

Even I I shut these off in those settings, the button starts up toggled on, hiding files.

Hmm. Does it happen to all folders? You could have a look in -> tools -> folder options -> filter [tab], if you have some checkboxes set. If so, try to uncheck them. Otherwise, i have no idea at the moment, what else to try.

See the Folder Formats FAQ.