To make the Save in Legacy Format command behave consistently to native Save, the Save dialog should be shown if the model is not already saved, letting the user select location, name and version.

As of now I haven't found a way to open the native Save dialog. According to the Ruby API documentation, Sketchup.send_action(21036) should work on Windows, but it does not.

Ideally the native dialog should be used, as a manually recreated one would not be automatically localized and in other ways risk not feeling like the native one. Also it doesn't appear as the version dropdown can be implemented in a custom save panel.

Without noticing I positioned the menu entry at the 9th index, with my own Open Newer Version extension having its entry further up. For this extension to be positioned between Save As Template and Revert, it has to be positioned one step up if Open Newer Version is missing.

Note that this is something of a hack, not a general solution. If another to me unknown extension places its entry anywhere above this extension's entry, this entry will be offset one step relative to native entries.

Continuing from #1, there is a risk the user intends to save to an older format, but press Ctrl+S out of old habit without realizing it, and end up all with succeeding calls to Legacy Save saving to the most recent format.

It may be useful with a warning saying you are doing a legacy save to the most recent format, not a legacy one. However, such warning must have a "Don't show me this again."-option, as some users may use Legacy Save as their default method of saving, regardless of whether they want to save to an older format or not.

As of SketchUp 2019 there is an API bug in Model#save. With version 2019 sent as a parameter the method throws an ArgumentError. This could be quite easily fixed by checking if the selected file version is the same as the running SU version, and call the method without this argument, as it defaults to the running SU version.

However, through my own experience with using the extension I've noticed that I often get this error when I intended to save to an older format, but had previously accidentally out of habit pressed Ctrl+S and saved to the most recent format. In such a case the error message reminded me to go to Save As and select the old version once again.

Perhaps, in addition to fixing the bug, there should also be a warning message when trying to save to the version that SketchUp runs at? However, such a warning would be annoying if you rely on Legacy Save even for saving to the most recent version, e.g. by relinking Ctrl+S to trigger it. Such a warning would require a Do not show me this again-option.