You can achieve this by adding some custom css. Tapestry uses good class names for you to target all elements. Just add some css with a higher specificity to overwrite the tapestry defaults.
The following will give you your desired result. You'll have to play with it a bit (colors, widths etc.) to get it fully to your liking but this will fix the layout for you.
body DIV.t-beaneditor-row {
float: left;
width: 300px;
}
body DIV.t-beaneditor-row LABEL {
width: 100px;
}