feature request: frame number placeholder in saver

I just rendered variations of a still image with custom file names which I had entered into the saver:

test_still_16.jpg
test_still_20.jpg
test_still_24.jpg

The number should indicate a parameter that I was changing. Upon finishing I noticed that there was only one file in my directory: test_still_01.jpg because each time I had rendered frame 1 only (since it was a still image).

Being a long-time Fusion user I should have known better. But I forgot that frame numbering in Fusion doesn't have to be separated by a period... Can we please, for Fusion 7.7 or 8 or whatever is next, get support for "####"-style or "%04d"-style placeholders?

For compatibility, Fusion could automatically convert to this syntax whenever something is entered into the saver's file name input. If (in my case) after closing the Saver's file dialog "test_still_16.jpg" would have been turned into "test_still_##.jpg" it would have immediately occurred to me that Fusion will overwrite my file.

Related, it would be nice if the render dialog, when you only have one frame as your range, show a checkbox to disable sequence numbering.

Basically I want the same functionality I would get if I right-clicked in the viewer and hit save image, but with the ability to set the options for the file output from the format tab.