@Grazie … it is an Envelope and works as @EricLNZ suggests - as per:
If you were thinking of another method via the post title of "install still frame', it would be great if you could expand on the circumstances of what you are wanting to do.
@Grazie … the only other way I know of - which is far from one step - is to place the cursor on the desired frame on the TL, and hit the 3.25 disc icon above the Preview Window (Save Snapshot to File) which then saves the image as a jpg or png as selected in the Save As window. Though I think that the process does it automatically, I do raise the Preview to Best/Full to ensure best rez. Since the intro of the Freeze Frame at Cursor, I have happily had little to no need to use the above process.
In Vegasaur there is the function "Freeze Frame", which makes the handling easier. At the cursor in the selected event a picture is created, the length of this stop can be varied without using the preferences, besides you can also split video or audio, etc. Basically the same thing Vegas can do natively, but more comfortable
There's a script in the HappyOtter Free Tools library, Insert Freeze Frame that adds a freeze frame at the cursor position or at Markers. Rather than futz around with envelopes, it creates a lossless png. Here's a link to a demo https://vimeo.com/392307916 and where it can be downloaded. https://tools4vegas.com/library/