Negative time is not really anything I would suggest. There are a few cases to have things before zero, but this should be limited to the preparation of data, not for anything rendering. In fact, you can set the project time to negative, but the rendering is limited (Render Settings) to positive numbers, starting with zero.
Hence why I created the txt files with the frame numbers. I can open the -1 to 2.966 example as text, but it will use only frame -1 to frame +3. Which means a few frames and 119 keys. Not ideal. When I set then (not before!) the Project to 900fps, it spreads, but it has gaps. I would not recommend this. I switched any snapping off, which sometimes deletes keys that want to snap to the same frame.
As you undoubtedly know, to add a column and fill it with 1-n for the frames is no problem. However, even if that works then with negative numbers, you can’t really use it in Cinema 4D.
I hope that clears it, and I assume you would like to have what you had in LW also in Cinema 4D.
You might check with the support. I stopped using LW in the mid-‘90s after a half year of testing it, so I can’t really remember how negative numbers have worked in LW6. However, I understand your wishes.
What comp app do you use? In After Effects, you can set any comp to negative numbers, and move the results of a positive only clip/sequence to that negative start. I haven’t used it at all in the past three decades in any production, so I can’t tell you what will happen. Which means I tested it, of course. An image sequence rendered with Media Encoder started with frame zero. No idea how to get it to show negative frames. I have to test others, but you might share what app you use, so I can check this.
Here is my negative test kit.
All the best
P.S.: a partial workaround, again, not recommended to work in negative numbers.