This seems like a weird solution to me. Wouldn't it be better to make room above the buttons?
It needs up to two lines when using a counter. And the tree button doesn't work when there are placeholders, so why not?
Because:
The position of the Tree button is inconsistent.
It's weird that buttons disappear from a dialog instead of getting disabled. Why doesn't the OK button disappear when there is an error in the rename mask?
The rename preview is randomly dumped in the dialog instead of designing a proper dialog.
I suggest:
Add a preview box below the input field which is disabled by default and enabled and used when placeholders are used.
Use OK, Tree, Cancel buttons positioned consistently with other dialogs.
Don't hide the Tree button. Disable the Tree button if you want, but I don't see a reason why i should be. BTW, why is it not possible to specify a drive in the mask when using placeholders? (In other words why is a colon not allowed?)
In the current design there are some problems:
If a placeholder is added and there is an error, the Tree button is not hidden. For example, first use the Tree button and then the placeholder button.
If placeholders are removed, the Tree button doesn't reappear.
