and there is no way to restore it
Actually, you may be able to restore this at least in terms of the affected field's appearance. Under the paragraph section on the inspector's appearance tab, you can specfiy left and right indents.
But in a quick test on Windows XP, I was unable to get the result you describe in your report.
Thanks for trying to reproduce on WIndows. Did you try using the FTS files or a new file from scratch? The latter seem to be 100% reproducible but when I create a file from scratch it's inconsistent.
With respect to restoring padding, there really isn't any way to do this. As has been noted elsewhere there is no place in the UI that allows padding settings for a field to be changed.
As for paragraph indent, it's a different setting. The difference can be visualized by turning on Text baselines for a given field. The length of the text baselines reflect the padding amount. On the other hand, the paragraph indent moves the text relative to the text baselines.
I tried this in a converted from Filemaker 11 file on a layout created post conversion with a "non classic" theme.
I just created a brand new file for demo purposes in Filemaker 12. Just now, I went to that file and:
Duplicated the layout to keep existing layouts unmodified.
Selected a text field and used the "hover" settings to fill it with yellow.
Returned to browse and tested the hover settings.
Returned to layout mode and copied the object style.
I then individually selected different fields of the layout and used the paste style button to give them the same "hover" settings.
The padding in each of these fields did not change, but they now fill with yellow when I hover the mouse over them.
The layout theme was Cool Gray.