Not at all, no. Mercifully once rows have been made, you can navigate from cell to cell with arrow keys. You'd think maybe we could at least make a set of rows in bulk, no. Here is text from someone's guide: You can enter data directly into the R Commander basic spreadsheet-like data editor. A simple alternative, which we in fact prefer, is to save the data in a plain-text file... and then to read the file as in the preceding section, via Data - Import data - from text file, clipboard, or URL... .
What's even worse is, if you aren't aware of the lack of usability, pressing the enter key will erase the data that you have just entered in that cell. You have to arrow (or mouse) out. Apparently you do seem to get to a new row in the process, so I conclude that you can create new rows by repeated pressing of the enter key, but do not do so after you have entered any data, because you'll erase the contents of the cell you are at.
(Edited 12 minutes later.)